Take your time mate, first establish the car that YOU want, spec included. Then spend time comparing prices around the country (via autotrader and other sites)...they can be very high in some areas compared to others.
Its worth veiwing a few before you even start thinking about parting with any cash.
I spent ages looking for my car(8 months), looked at at least 10 I reckon and there was always something I found that I knew would niggle me if I brought it. (be it higher mileage tahn I wanted/little marks or a scuff mark etc)
Eventually I found the one that was just right, Mint condition, VERY VERY low milege, Top spec. And knew I had to have it. If you by the first one you see because of convienience I can assure you that a month or 2 will pass and you will see better one for sale somewhere and you wish you would have waited.
When your spending a decent amount of cash on a car, you want to make sure you dont start regretting it after a short amount of time.
So my advise would be, be patient, do your research and the right one will come along.