The sizes of the nuts are thereabouts, just off the top of my head I remember them being 21's but they could have been 25mm.
As well as the wishbone, you'll need a new bolt from the stealers. approx £4 or so.
Basically the wishbones are assembled from new onto the subframe before it is bolted onto the car. The bolts are dropped in from the top. As a result, when you want to remove the rearmost bolt, it fouls the chassis and you cant get enough clearance to withdraw it.
Solution is to undo the nut, and tap the bolt up enough to get a junior hacksaw in to cut below the bolt head. it doesnt take much cutting, but allow a good 15 mins or so, for swearing time!
Once the heads been cut off, the thread can be tapped through from above. I used a long pole through the engine bay, theres enough room to do it, could even be done with a small punch.
Once its out, the others are quite easy to do, the tapered one might be a pain but there should be an allen key hole in the thread to lock it off, it should stop it spinning when you're tightening it up.
I found it easier to put the subframe bolts in first when assembling the new wishbone, as otherwise the thread holes in the bushes wont line up. get these lined up and a bolt in each first and it'll be pretty easy.
If you dont fancy that, you'll either have to remove the whole subframe, or pay someone £70+ to do it. But trust me, its not worth £70 its only half an hours work despite what anyone might tell you