After a lot of research I decided to buy my batteries from Barden http://www.barden-uk.com but then I was looking for high quality branded deep-cycle batteries.
Apart from truck factors, you can also get a huge choice of batteries from Adverc. On their battery page, search for "Flooded-Wet" construction and "Deep Cycle/Cyclical" application - you'll find Numax HGV Commercial batteries at £65-£75.
I paid £60 for 100 amp hour battery, which is deepcycle, but confusingly has both round car type posts and flat bolt on type connectors.
Has been deep discharged several times last summer due to the beer cooler (fridge) and also was used to start a 20 HP BUkh engine whose own battery was flat
Chris, Lincoln Batteries Ltd , Sou'fend. Super Outfit, very helpful, and very,very competetive! They manufacture to whatever size you need & which cycle type. 125 amp hd truck type about £50-60. Offered me a 375 ah but couldn't lift it! HTH Tony W.
Small correction - LINCON batteries, on the Arterial Road almost opposite Camping and General /forums/images/graemlins/smile.gif
Also look at Battman.co.uk - they were cheap and quick too.
As some have said in other posts. Go to a battery specialist. (phone book) I got (in the UK) two for the price of one (Chandlery) that way. And if they are local they can check them/it for you each winter. My supply attacherly came to my house to do it!!
It's out of your area but previously I have always purchased from Barden but they couldn't get close to these guys, CPC Batteries, http://www.cpcbatteries.co.uk/ who were both helpful and friendly and delivered to me in Wokingham from Middlesex.
Can't say they'd go to Essex but really worth a try. I purchased four gel batteries, two start and two deep cycle.