Well I am having an argument with myself now over whether I want to go for a Jazz sized car or stay with something the same size as I have. I am comfortable I can do without 4WD through sensible tyre choice but I do value the increased ride height, since it is very good for my back and also for driving around the country lanes I use every day - both in terms of visibility and capability to get off the road when passing in tight spots or parking in remote locations.
So, given the only issues with my current car are it is now in it's fifth year, it is realistically only capable of around 40mpg, and it 'felt too big these days', and given otherwise it has every feature I would want from a replacement, and it is already set up with Nokian All Season tyres all round, I have decided to wait another six months and resume looking in the Spring. By then there should also be a wealth of nearly new Jazzes to choose from.
Thanks for all the input folks.