Glad you're not putting it on the mortgage.
0% cards might work for you, but remember that most of them charge a fee now for balance transfers, so unless you think you'll be able to pay it all off in a single 0% period, you're probably better off looking for a more standard loan.
If you go down the loan route, by all means talk to your bank, but you'll probably be able to find cheaper deals via the net (Egg, Nationwide, Carhoot etc). It might also be worth looking at Zopa
However, if it was me, I'd still be tempted to go for a flexible loan. £5,000 at, say, 7% over 5 years is going to cost you just under £100/month (calculator ), and you may find with a flexible loan you're able to pay it off sooner (5 years is a long time - I've got a non-flexible loan and wish it was flexible!).