It seems like in London the only paid options on backpage that work are the manual bump to the top of the listings and the add multiple locations.
The sponsored option seems a bit pointless. There are so many sponsored ads that they don't all fit in the sidebar and the excess is in the sponsored section at the bottom of the page so counterintuitively, you'd be paying to have your ad below the free ads.
The auto-repost seems to happen in hourly batches so your ad might never actually get bumped to the top this way. It will just get bunched in with the other dozens of ads that chose that auto-repost hour and that batch will go to the top. Clients wil only look at the top few ads and seem to only look at the pic and the contact number so getting bumped to the 20th posisition won't get you any calls.
Manually bumping your ad the the top does bump you to the 1st position right at the top of the ads and this does get you a spike in calls and doing this multiple times per day will bring in jobs.
I added the additional locations from around London like Oxford, Surrey, Brighton etc and when I got calls I said I'd travel to them if they paid a deposit and got a few jobs that way. It made me wonder which added location I'd get the most calls from so I added all the UK locations. A lot of calls from Belfast. I talked to a wG friend about going there for a few days and added Belfast to her ad too and her phone rang non-stop so we went for 2 days and were both very busy there. (After checking into our hotel, a client told me we were staying in the most bombed hotel in the world
)