Am I being taken for a ride?

[BByTheSea]

I could use some genuine advice please. I employed a plumber to check why my boiler was leaking. He has been 4 times now, replaced the expansion vessel, PRV, o rings and washers.
He messaged last week to say leak was fixed but when you put the hot water on it was making the radiators hot. He went back today to fix this, said he’d put a spring in the wrong way. Today I’ve found out that the only way I can get hot water is to have the heating on. It wasn’t This way before he stripped the boiler! He text me tonight saying he’ll call the boiler manufacturer Monday but that it’s more hassle than he wants or needs.
So my bill is at £700, and from what I can tell he’s made things worse not better. Am I being taken for a ride? Should he now be solving this on his own time or is he right to expect me to keep paying him for these visits? I don’t know how to proceed but can’t afford to keep paying huge amounts of money out to no avail. Any advice please?

 

[Ric2013]

The breakdown seems fair enough, and my impression is he's being honest enough but struggling with the job, possibly doing quasi-engineering work that merits double the hourly rate he is charging, but not quite up to the task, so taking a long time or making mistakes in the process?

 

[Dr John Doolittle]

Are you considered to be vulnerable? If so, I'd contact trading standards, the police and the body that gives him the ability to self certify his work. This man needs removed as he either has no idea or is deliberately defrauding you (criminal hence the police)