The easiest tortoises to keep in the UK are Iberas, Hermanns & Marginated tortoises. Here are some links that will hopefully help:-

Care sheets for tortoises:-

http://www.tortoise-protection-group.org.uk/site/80.asp

(please click the links on the left hand side of the page for each species)

List of recommended UK Breeders:-

http://www.tortoise-protection-group.org.uk/site/70.asp

Just about all tortoises sold by pet shops are imported, which can be very stressful for them and many arrive into the UK with parasitic infestations and other problems; dehydration, hepes etc

Ideas for enclosures:-

http://www.tortoise-protection-group.org.uk/site/58.asp?thissection=17

Despite what pet shops promote vivariums are not suitable for tortoises, they offer only one temperature (a tortoise requires a range of temperatures) and they are far too humid for most species of tortoise.

Heating/lighting

http://www.kimbosreptileworld.co.uk/megaray-120w-self-ballasted-p-145.html

There are various lamps on the market, though most tend to use the above

Lamp holder:-

http://www.kimbosreptileworld.co.uk/clamp-lamp-p-34.html

Diet:-

http://www.tlady.clara.net/TortGuide/Diet.htm#plantlist

http://www.thetortoisetable.org.uk/site/tortoise_home_1.asp

HTH
Kindest Regards

Darren