I was in the same boat as you last year and decided to bite the bullet and go for it... Other people have already mentioned the costs of the tests, they are standard, Kit wise:

AGV K4 helmet, £180
Boots - I got some TCX waterproof boots for £179 and they are superb, never been cold or wet
I went for RST Razor jacket and trousers, they are seperates but zip together, also come with thermal liners for both parts, so even in the pissing rain on the M25 i've never come home cold or wet
Gloves - I cant recommend the "Bikers - Koln goretex" enough, £90 so a bit steep but worth every penny, nothing worse than cold fingers!

I bought a Honda VFR as my first bike and have used to commute in to central london no problem, Tax is £72 a year (ish) and I pay £33 a month insurance. The £23 full tank is good for about 150 miles... Only paid £1300 for it last November, good time of year to get a cheap deal... Micron exhaust was £100 off E-Bay! It has its first service under my ownership this weekend (bought with no service history!) so hoping for no suprises!

As mentioned above, my initial outlay was huge, probably spent as much on kit and learning as I did on the bike... Kit alone was £640