I have been in car audio retail for over ten years and as you can imagine we see all sorts of stuff bought off ebay through the door. Firstly there is a lot of very cheap Chinese stuff about, no problem but check the following. Will it hook up to the steering wheel controls of your car (volume, track selection etc) if you have them? Does it have a European compatible tuner section (Not American or Asian)? Do the leads have an ISO plug on that will either fit straight onto or easily adapt to (Using a readily available ISO adaptor) your car or are there just bare ends? If buying a fixed navigation system out of an imported car do not fall for the old' It just needs a UK disc' ruse. Also be aware of many copy/fake products. If you see a brand new Focal speaker component set that normally sells for £99 at £29 then it will be a copy, it will look the same but sound rubbish and fall to bits in use. If you buy proper branded products (Alpine. Kenwood etc) make sure your warranty is with the supplier do not fall for 'Just take it to your nearest dealer, they have to sort it', no we don't (and won't) your warranty is with the company you bought it off. NEVER deal with a company that does not have an address and land-line phone number. Emails are very easily ignored (just press delete!). I kept this short and hope it helps.
Good Luck !
Paul (Speed of Sound).