Advice needed.

I am taking part in the Silverstone track day next month & the car is due for it's annual service around this date.
I have only done about 4k since the last one & the oil is still clean on the dip stick & have no problems.
Do I have it serviced before or after the event
Also after a decent run, the level in the coolant bottle rises by about 2". Does this indicate that the
system needs bleeding?

Presuming you are running with fully or even semi synthetic oil it should be fine ether way, however I personally would change it after the event. Your engine has not done to much work on that oil so running it a higher temperatures on the track won't hurt it and afterwards you can have fresh and a chance to check no derbies were dislodged during the run :beer:

The rise in coolant level could be a dodgy pressure cap.:shrug: