In reply to PPP:
Go Outdoors and Decathlon both stock cheap, relatively comfortable climbing shoes for £30 - £50. Try several different styles to see what works best for your foot shape. Most shops have a wee wall with climbing holds on so you can try the shoes on the way they were meant to be worn - they're not for walking in!
I personally find Red Chilli shoes uncomfortable and awkward to climb in, but get on well with the shape of Evolv and 5.10. Other people's feet are different. I haven't tried Decathlon's Simond brand.
As to sizing, climbing shoes are designed to be worn without socks. You ought to get a pair that is the same as your normal shoe size, but as the fit is so close, many beginners find this uncomfortable which is why climbing wall hire shoes are often given out at least one or two sizes large. After a few sessions climbing, most people find that they prefer the closer fit as their feet will be better supported, and having no dead space between the toe and the end of the shoe means that feet stay on small edges without slopping off. It is normal for toes to be slightly bent when wearing climbing shoes but the shoes should not be painful to wear, and certainly should not cut into the achilles tendon at the heel.
£30 is definitely the bottom end of the price range for climbing shoes - most are now at least £65/pair. After 15 years of climbing, I just get ones I know I will find comfortable to wear for long days as I know the aggressively curved banana shoe styles won't get me up anything harder - if I want to improve my grade I simply need to get fitter - and I woudn't normally pay more than £50. For the last couple of years I've been wearing Evolv Defys and they do the job for me.