Hi Jez,
hope I'm correct you want to learn more abt the Yemms before 1841 Census ?. Unfortunately the general local Government BMD & National Census Records only start after 1837, before that individual Parish (Chapel)Records have to be studied as far as I understand it all. We are so very lucky the FoD is covered by this site's huge database in this respect (maybe there's a similar site for your Teignmouth kin, try Googling for it etc). Apart from the PRs there are other lists etc which can be used but this varies enormously from place to place, such as the Bigland Transcripts recording Church graveyard tombstone inscriptions whioch were started in the mid 1700s, Ruardean is one of those Churches covered,
see http://www.forest-of-dean.net/?Memorial_Inscriptions_Bigland_Transcripts
Also see
http://www.forest-of-dean.net/?Memorial_Inscriptions
Again the tombstones would usually mention close family of the buried person, so helpfull to us wrt recreating the family unit.

Have you tried using the very nifty Advanced Search feature for this site, from the icon at base of the Parish Records Search page, its a real boon !. It takes sopme pracising to get the hang of it, but if you know a particualr surname or Parish, for example, you can soon get a feel for that family's heirarchy. Apologies if you've tried it, but if not here goes...

eg click on Advanced Search, it opens to a Baptisms search page. If you use the dropdown menu this can be changed to Marriages or Burials. You then enter what you know into the relevant boxes, I recommend entering as little as possible to get the maximum number of possible "hits". The Adv Search is great if, say, you only know one name in a Marriage, or one parent, etc. This search also caters very well for name spelling variations.
eg Using Baptisms search page, click "Search" button to get "search for records" page. Enter as little as you like in one or more entry boxes. (Like many search engines, often "less is more", you can easily scan thro lots of results and pickout those that maybe relevant; apply to many input filters and you may easily miss important relevant records).
So for fathers surname just enter "Yem", this will find and list all such names so will find all Yeme, Yem, Yemm etc. Then enter "Th" as father's forename, it will find all variations of Thomas, Thom, Thos(the old abbreviation) etc etc. As I said if you practice you'll soon get the hang of it.
Now press search, it will display a list of results after searching the hiuge database from this site. In this example it gives 92 hits, displayed in a table.
Now you need to get all, or as many as possible, displayed on one page; click "100" on the dropdown menu for "records per page". Now its wise to check they are all sorted logically, my preference is in chronological order; click on the "year" heading and the table will be sorted in year order.
You can see the majority of early (pre 1811) Records are in the Ruardean area, as you'd expect.

By carefull studying the results you should be able to discover patterns ie family groups etc. In this case it's easy to see that Thomas was a partiocularly popular/traditional name for the Yem family, in later years such clues can be useful when trying to sort out individual family groups who share a common but unrelated surname, say.
Yes, you could have also entered the mother's forename, such as Eliza to cover Eliza and Elizabeth, but what about Betty, Liza, etc ?.
Best not to enter the mother's surname as most early PRs didnt include this, thereofre this potential "hit" won't be displayed...again experiment and see for yourself, but always remember "less is more".

So, from these results and looking for mother Elizabeth, you can find the following Baptisms, you can cut & paste them like this, or if you click on the lefthand
Record ID it will display each on a separate page.

55418 1788 YEME George, Thomas & Elizabeth Ruardean
55473 1790 YEME Richard, Thomas & Elizabeth Ruardean
55551 1792 YEME Thomas, Thomas & Elizabeth Ruardean
55659 1794 YEME Ann, Thomas & Elizabeth Ruardean

(If you look down the results table you'll see another later Thomas/Elizabeth pairing, there are other mother's names either side of Elizabeth but you can easily see this is a likely couple's family as their Baptisms are all in the same locality and timescale, in this case Lydbrook, and so on...)
So, unless I'm mistaken we've found a new likely sibling for your tree, Ann.

Remember in those days it was normal to name firstborn sons after father (Thomas no doubt!) and similarly girls after their mother, always look out for such a clue.

If you now repeat your search but with the Burials, unfortunately you have to re-enter your input data but thats a very small price to pay ! This time by inputting "Ye" for surname, and "Ruardean" for Chapel, you get 166 PRs to sort & study, back to 1538 !!. Luckily for you Ruardean Church dates from the C12th, so one of the very earliest Dean Parishes alongwith it's near neighbour Newland, hence this wealth of very old PRs for your line. In later years as more parish chapels were built to cater for the growing population you may need to look at nearby Walford, Bicknor, Lydbrook etc.
See http://www.forest-of-dean.net/joomla/the-forest-of-dean/maps-of-the-forest for the early Parish areas, a sense of the local geography is usefull when searching your likely ancestors.

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