If it was me, I'd use the money as my contribution and finance the rest.....say up to an £8k priced car. The £3K (approx) on finance over 3 or 4 years would be circa £100.00 / month, nowt in real terms considering the Zed isn't a cheap daily car. That way your (hopefully) buying a gid yin and will have been looked after. Even better idea, buy from an established member off here who will probably have a build thread on their car.
Lots of abused Zeds around due to them getting more affordable of late so go in with your eyes open and perhaps even get a member off here to go view a couple with you, plenty of members up and down the country willing to help and be prepared to travel for the right one. Gid luck