Im almost in the same boat.
I should be able to get around £1.5k for my current car, but I want to keep that for inurance etc on my new GTI! Im on a time scale though since my current car needs a few jobs done to it, including a new exhaust at some point due to some minor signs of corrosion showing, new wishbone bushes, and the coolant is starting to leak from somewhere I think! The coolant is the only concern, s the others have a good year or so left in them yet. I dont want to spend the £4-500 on the repairs etc if Im selling it anyways!
Im looking to buy around Mar/Apr/May time, but am looking around at price etc. Currently I have almost £12k saved, but I want an Edition30, with a few options on top, so Im expecting to pay around £15-16k I reckon.
With your £10k you should easiy be able to pic up a standard GTI.