No need for a FAO - Iv'e spotted it
Well I'd say a good place to start is ..... ANYWHERE
Prices range from £30 for a part day - to upwards of £400
You can book most trackdays online now - or certainly on the phone if your unsure about online methods. A circuit based trackday will offer the best facilities for a new comer, both in terms of safety, and organisation. Most of the circuits and or organisers are members of ATDO
http://www.atdo.co.uk
If it is your first trackday with a newly built/prepared car try to keep it local, until your confident about the car.
Dont bother too much about what everyone else is doing - concentrate on what you have - and what you want to achieve.
If possible try to get out as a passenger for a few laps with someone if you are really unsure of the venue, this will settle you in, and you will begin to learn the circuit pretty quick.
Remember its not all about speed - you don't have to try and keep up with the car infront - its not a race (as racing is not allowed) just go at a pace you are comfortable with, and getting the most ENJOYMENT from.
Try to get to one of the days that are published on here - we are all loonys and will offer more personal help one to one, rather than through the keyboard.
Anything else ? Just ask

What car have you got ?
Tony