Hi Digger, at the time of writing this there was no other replies but with the moderating process there may well be by the time the posts go up. You maybe should have posted on the main page of the forum where you would have got a better response.
Insurance is a nightmare and it's just not worth taking any short cuts with it. It's usually based on your turnover but as it's your first year they will probably make a figure up and charge you on that basis. Shop around, one of the suppliers is a forum sponsor but there are others floating around who may have already PM'd you. Make sure they have a good rating as it's easy to get caught out with the price, like everything else cheapest is rarely best. If you have self employed, make sure they carry their own insurance as they will pay a lot less but again make sure you inform your company as some just don't like too big of a percentage coming from subbies but it will make a difference. Also make sure they give you their CIS details as that could go horribly wrong very quickly and keep meticulous records of all deductions and yes, you will need to register your firm with the tax man and maybe the VAT man depending on your level of trade but with 2 subbies that would be enough to tip you over the threshold no problem.