The 1.5kva transformer on the lawson website it pretty good value, especially if that includes delivery!?
Apart from the PC and transformer, you'll need a velcro/hook&loop backing plate, but depending on where you get the PC from you might get one included. A few of us UK Autopians have the 5" flexi backing plate available from the Autopia shop for $16 (purchased at the same time as the PC).
Also you're gonna need some pads, as you can't do anything without them! Which ones you buy really do depend on what condition your paintwork is in. My paint is in excellent condition so I didn't bother with a cutting pad, I just got 2 polishing pads and 1 finishing pad from Alex to get me started. £12 GBP each I think.
You may or may not require some sort of extension lead, but I'm not gonna open up that can of worms again!
I think that's it.
My grand total comes to £220 including an extenstion lead that I've currently got on order.