Parkers reckons £5665 with 30,000 miles from a dealer, so maybe £5000 would be about right with 41,000 on it.
On the other hand, if you get the dealer to knock nearly 20% off the value of the car, then you're doing very well.
In fact, if you do manage that, when I next buy a car, can I hire you as my official haggler?
Id say £4500 is a fair price for that car. £5k if its got leather. If its in an alfa dealer expect to pay a price completely out of touch with reality... if its in any other dealers stock you stand a good chance of getting a deal as nobody in the trade likes an old model alfa hanging around. Bid hard & good luck!