In reply to Shugs81:
No point waiting to get fitter, jfdi.
You don't need a harness for boulering, you can hire one indoors, get one when you want to climb outdoors or when you know why you want one.
Shoes. This is a big debate...as you've seen. You can hire them, but they can be minging. Take a spare pair of socks. When you get your own shoes, then you'll prolly wear them without socks. Generally the first thing you buy as soon as you decide you want to carry on.
A beginners pair will set you back £50 - £70, less than that if you can find an offer. You HAVE to try on the pair you're going to buy, minute differences in size are v important with climbing shoes, you need to find a make that fits your feet (not a make that your mate likes). A shop will help, find one that has assistants who climbs.
Chalkbag will set you back around £10. Belay device will set you back £15 or so. You'll find out what they are on your beginners course.