I'm pretty new to this club and was in the same boat as you.
I'm 25 and last year had a 2010 Focus RS that i used as a daily runner and on track days. The RS was getting too expensive to run for both so i decided on a Westfield for track and good weather, and bought a BMW 120d as a daily runner.
My Westfield is a Megablade and set me back £10995. It has roughly 130bhp and trust me, its more than enough for a first Westfield. My RS was 350bhp and felt relatively pedestrian compared to the Westfield. The insurance through Adrian Flux is just over £500 a year, tax is £75 for 6 months.
I bought a fibre glass helmet for £50, haven't bothered with the wet weather gear as its got a full cage and aero screen so only gets used in good weather.
I also wouldn't consider myself a mechanic in any shape or form but earlier on in the year my engine went bang. I bought an engine and swapped it on my own with just a halfords advanced tool set. I was a bit scared at first at tackling the job but once i got into it was surprised at just how easy it was. The first time i had ever tried swapping an engine and managed it in one day.
Before getting the Westfield i was a bit sceptical at just how much more fun it could have been than my RS, but trust me, it's in a completely different league.
Do it, You won't look back!!
Tom