I just recently made the move from Virgin TiVo to a Humax Foxsat PVR. Luckily the previous residents had Sky so no additional outlay was needed.
I do miss some of TiVos features, like Wishlists and Search, but find I'm not missing the extra channels (I was on TV XL) as most of them I never watched. Another thing you might miss is Flimflex.
Worth taking into consideration is whether to wait for
YouView enabled Freesat boxes, which would give you all the Catch-up TV services, though it's release date (in time for the Olympics) is prone to slippage.
For someone who doesn't watch a lot of TV like me (and sticks to the five terrestial channels), and doesn't use VoD or Catch-up, I can say it's worth making the move to Foxsat.
As to buying the box, I bought mine as A-graded stock off the Humax web-site. It worked out cheaper then Amazon, and the one I've got seemed like new.
Here's a a link to the Manager's Specials on Humax's site.
(EDIT: Didn't realise the thread was four days old - hope it's al-right to post one more to the end)