Hi Oli
Welcome to The Tortoise Table and many congratulations on acquiring your Horsfield (what's his name by the way?).
He really is a lovely looking little fellow (or girl -- too early to sex at this stage), and well done for switching over to a tortoise table -- it will certainly prevent problems later on. When you are making his table, I would get the largest that your space will afford, as tortoises do need lots of room and they get bored in a small space (and if space doesn't allow for a big table then a ramp leading up to a second level can provide more interest and exercise for them). Tables are very easy to make (just think of a set of bookshelves lying on their back, with the shelves taken out). Also, if you have only just acquired him you ought to be able to return his viv on the grounds that it is unsuitable for this species of tortoise, and we can provide you with documentation to prove that. If not then I've attached some photos and a link to an article on converting a viv in case they are useful.
https://www.thetortoisetable.org.uk/tor ... 3xK8O3TWNI and also to our article on making a tortoise table (this is one for babies, so you might want to make a larger one:
https://www.thetortoisetable.org.uk/tor ... 3xMOe3TWNI
[attachment=0]Viv Conversion.jpg[/attachment][attachment=1]Viv conversion.jpeg[/attachment]
In the meantime if you can take the doors off the viv and put up a board just high enough that he can't get out, that would help.
I'm not sure what substrate you have, but tortoises do best in a soil and sand based substrate (so ordinary topsoil and children's play sand mixed together is ideal, and you can buy bags of both at most garden centres, Homebase, etc.).
The other essentials are a good UVB light and lots of calcium (if you want to know more about those, let us know and we'd be happy to go into detail).
Re his nails -- they look a little long, but not really bad, and you need to be careful about trimming them, because like birds they have a vein running up the nail and you don't want to inadvertently cut through it. If you put a slate or a nice big piece of limestone down for him to walk over, that will help to keep them in trim, but he is so small that unless his long nails are actually interferring with his walking then I would leave them.
Horsfields are a burrowing species, so those nails will also help him dig, and it's also a good reason to have a nice deep substrate so that he can bury himself completely if he wants to.
You probably already have one, but in case you don't then here is a link to a care sheet for Horsfields:
https://www.tortoise-protection-group.o ... 014New.pdf
Nina