Ironically, after I'd posted my question I realised that I have a length of massive electrical trunking in my shed which I bought years ago to house water pipes. This will be very suitable for the task and, yes, maybe a 45 degree slope is a bit much, 30 degrees might be better.

As for is it for handing money to prostitutes - no! I bet they take contactless payments these days - although I'm not sure what £30 would get you in the way of sexual services?