Can anyone tell me whats a reasonable amount I'd expect to pay for one on
> e-bay or whatever?
>
> Original radio was a Ford 2006, how much for the same or similar 2nd hand?
I'm afraid this falls into the category of "Stop Being Lazy and Look Yourself" A quick flick through the Loot, E&M, FindIt & eBay websites should turn up some.
For example there's a 2006 on Ebay that finishes tomorrow, no bids and it starts at a tenner; BuyItNow for £30. Another finishes at 8pm and is only at £16.