"Can anybody tell me wether it is a good idea to keep 2 horsfield together or not, are verry social or solitary? It's just i've got 1 at the minute and I was wondering wether it would be a good idea to get him a friend or not........ Or can you put them with any other species (sorry if this is a stupid question!)"
these are not stupid questions at all. in fact, you'll get different answers to each of them.
tortoises are not social in the true sense of the word and do just fine by themselves. russians can be kept together as long as there is room for them to escape each other if necessary, there are some visual barriers, and a few places to hide and escape from persistent males. even feisty males will eventually get along as long as they are not forced to be in each others' faces.
i keep a breeding group of 9 together (with 4 adult males) and never need to separate them. however, they are in a very large outdoor enclosure with tall grass, multiple hides, and a few small hills.
hope this helps,
matt