It's rammed floor to ceiling with race and rally programmes, contemporary magazines, papers, brochures etc etc. I'd been collecting stuff on my car for a while and wasn't that optimistic of finding too much here but was pleasantly surprised. Got quite a few new race programmes, a hillclimb programme and some copies of Motoring News I was missing with mentions of the car in and even got a brew whilst I searched (plus found quite a few bits on other people's cars whilst I was there) .
There's not much room to move about the store rooms to say the least but it's a must for anyone with a period competition car who doesn't want to keep watch on Ebay for long periods looking for mags and programmes. Yes you'll probably pay more but they're open to a deal and any swapsies. If you've a lot of history to search for make sure you allow plenty of time, take a flask and a warm coat (very little heating!) , the hours will fly by!
I have bought a few pieces from their ebay listings. They are always as described, carefully packed and sent promptly. As Pete says some thing are a bit pricy, but were would you find another.
Nice articles on VPR 470 and GRX 309D in March 3rd '66 edition of MN. Also spied a few Llandow programmes with EOP 88D on the cover, just not enough time to go through everything. Some of the race progs are great if the results have been filled in, some right down to the DNFs! With alot of old mags now becoming expensive like Small Car and Sporting Motorist etc it'd be worth a trip just to spend a day having a bloody good read!
Found a little write up announcing the introduction of the Unipower GT with a shot of one of the first cars built in 1965 and the story that it was all the brainchild of Andrew Hedges and plans to sell kits at first. Not very accurate!
(very little heating!) , the hours will fly by! 
Great what you can dig up.