Hi Matt,
As beale said, find out what classes your local club runs. For instance, our club runs 13.5T 'Boosted' (ESC timing allowed) and 17.5T 'Blinky' (no ESC timing allowed).
If you only want to do 'Blinky', then you can save quite a lot of money by just getting a Hobbywing Xtreme Stock ESC, or even a Hobbywing Justock ESC. These are both cheap and cheerful ESCs, the Justock in particular is very cheap but still very good.
If you want to do 'Boosted', then the Xtreme Stock ESC is a good starting point, as is the SkyRC Toro TS120A ESC.
Motor choice - I would go for a GM Race if you're racing outdoors, they are far and away the most popular choice at our club -
http://www.rccarshop.co.uk/index.php...motors/gm.html - these motors have proven themselves to be very durable and reliable. Worth the extra tenner they cost over other motors.
Where are you planning to race, by the way? We're at Cotswold Airport, just outside Cirencester in Gloucestershire.