I think £2900 is a bit low Eric, we're down to very few 2.7 Sterlings now and not many 827 coupés either.
According to howmanyleft.co.uk last time i checked there were something like 81 827 coupés (quite a jump from 30 when i first got mine 3 years ago) and they stopped listing the 827 Sterlings as a separate model about 2 or 3 years ago, lumping them together with the 827SLi models.
Not many of them around either so there are very few of anything 2.7 powered these days, especially in nice condition as yours is and mine (mine should be, needs a bit of TLC at present though) and let's face it, where are you going to find another that's had everything done to make it reliable as you have?
Mine has also had everything done but it's not for sale so that's one less in the event of anything happening. I also happen to know one member on here recently got an agreed valuation of £10k on his Mk1 820Si, also certain insurers (Adrian Flux being one i think) value any 800 as being worth at least £2000 as long as it's roadworthy. Anything nice, rare or has a uniqueness about it for whatever reason (obviously not a uniquely shaped rust hole in the sills!

) has to be worth something more.
Besides, 827s are now rarer than Bugatti Veyrons and look how much they cost! Just to put that in perspective, there were 175 Bugattis on the road when i checked recently against only 81 827 coupés - i didn't check the total of 827s regardless of trim level so perhaps that statement isn't wholly accurate but can't be far out.
If it helps with your agreed valuation quest, i was recently offered £5k for my coupé by someone in the street and when i wouldn't sell and he learned i also had a Sterling, he offered the same for that, sight unseen.
If i were you i'd be pushing for at least £5k Agreed Valuation, sure you can pick them up on ebay for a few hundred quid but by the time you'd had everything done to get it up to the same standard you'd easily spend that £5k just getting it right.