If you're on this kind of budget yet still want a couple of punts a month I would say go for 2 x 30 minute bookings at £60 each. This is about what I'm doing at the moment as I have a similar budget. I know you said you'd rather have hour-long sessions for £60 each but obviously there's a lot more choice available in the £60 for 30 minute price-band. I've never punted for 1 hour @£60. I have paid only £70 a couple of times for an hour in the arse-end of London. But in London, decent girls in this price-band are hard to find and the few there are, become very busy.
I really try to make the most of my 30 minute bookings, that means, no shower at the WGs flat, no massage when you get there. Just straight down to business and hold out for as long as I can. If I feel like I'm close to cumming I'll stop and change positions, go really, really slow for a minute or two, or as long as it takes to lose the desire to cum. I'm the clock-watcher. Well, wrist-watch-watcher. I want to cum once only. I could cum in the first 10 minutes but there's no way I'd be able to do it again within the next 20 minutes after that. So I aim to hold on until the end. Wait for the knock on the door / her phone alarm / her nagging me that there's only a couple of minutes left, then cum. Well it doesn't always work out that way but the more I practise the better I get at it!