Homeserve/Checkatrade will start your first year at a lower price, but once you've licked customers rears to get great feedback over the next year then homeserve/Checkatrade will significantly increase your fees.
I did have a nosey on their website and was suprised how many new electricians have joined and are in my local area (far more than there used to be). Almost all have recently joined and very few have been on there beyond last year (a fair few with less than 10 feedbacks). When homeserve took it over they got so greedy that many loyal tradespeople who had been with them for years weren't prepared to be ripped off and left.
I haven't noticed any adverts lately for trustatrader, but I also had a nosey on their website and hardly any electricians local to me on there compared to Checkatrade, and quite a few recently joined ones. I guess trustatrader is cheaper than Checkatrade, but no idea if that's worth joining.
I was on my builder for 2 or 3 weeks and that was long enough.