If price is important to you, try a youth hostel. There are several in central London - you can find more info at www.YHA.org.uk.
Or if you are a friendly type, look for a home stay - people who offer rooms in their family homes. Just google home stay and you'll find them.
Premier Inn has a good reputation. Having heard from a few recent visitors, I'd avoid Travelodge.
www.expedia.co.uk has a good search engine. And don't forget about the tourist information service - they can signpost cheaper accommodation like guest houses and b&bs.
Good luck - hope you enjoy your concert, who are you going to see?
Laterooms.com works pretty well for me in London - being honest, most 3 star London bedrooms are smaller than the Premiere Inn ones! Premiere Inns also have decent mattresses and all the things you really need. However - London Premiere Inns are expensive, despite the claims. Here's a handy trick. Their room prices are based on dynamic pricing, so to get the really cheap prices you should put into the search box a 3 day stay, this will give you more chance of getting the cheap prices, and their rules let you cancel two of them, before lunch on the first day. If you just put in the day you want, the cheap rooms have always gone.
If you use laterooms, enter a postcode for one of the theatres, and it will then give you a map of those with rooms available. It won't be cheap, however - central London rooms are going to be £80 per room this time of the year - my one this week was £99 - no breakfast, and tiny compared to Premiere Inn, and no aircon.
Hi There
We often use lastminute.com and opt for their secret hotel. You wont know exactly which one it is but its usually fairly easy to guess cos of its nearest tube station. We've never had a bad one. Its also worth trying ebay....some real bargains x
I just recently paid nearly £200 for a room at the park plaza hotel ,one night no breakfast!!!!!! was a lovely room but didn't quite have the view i thought i was paying for!!!