If you think life's tough, guess what - it is! - If you think life's easy, guess what - it is. There is plenty of well/ correctly paid work out there to be had - you just have to change your mindset. Know your strengths, sell them.
We always allow two days for a swap to unvented, you just don't know what problems your going to hit (I actually asked the same question as this headline about 2 months ago, thinking it was taking us too long and we were doing something wrong) - as it happens we are back in with the same customer replacing all their heat emitters (16 of them), precisely because of the quality of work and care that we took with the work first time around.
p.s. GP' clear about £100k / year thats £300/day every day even when they are on holiday.. no materials, no insurance, no VAT, no accountant..