Unless you can get it for less than £165 inc postage I would use Midsat as you have a proper point of contact if anything goes wrong.
Be aware you have to sign up for min 12 months HD subs wherever you buy from despite what ebay sellers claim.
Sky don't care where the box came from or who installed it. You won't have any issues with them.
I connected mine up yesterday, did the forced software download and service menu/callback bits and called sky. No problems whatsoeve.
Be aware that the forced software download bit only updates to the last version before Anytime so the box will shutdown and update itself later.
google for midsat as i'm not sure if i am allowed to post a link.