Low pressure taps on high pressure system?

I have just had a new combi boiler system fitted and the boiler fitter did not change it over to mains flow, leaving a poor flow around the house. 45mins? + to fill a bath and over a minute wait for hot water to reach the kitchen. His reason was because our bthroom fittings are designed for low pressure system and that it would be best to do this when our new on suite and downstairs toilet get fitted in a couole of weeks time? We are not changing the main bathroom which has the same fittings so I am wondering what will haooen to them when it changes over? Do these need changed or can they rrmain the same? My bathroom fitter is now in my house and can't believe he didnt change it to mains and has left it too him, he feels the boiler fitter did not finish the job and also his quote didn't allow for changing mains. I have a couple of questions?
Has my boiler fitter finished the job, is it ok for him to leave the boiler not fitted to mains as my bathroom fitter has advised currently i wouldnt be able to get the pressure back in the boiler if something happened bcause there isnt enough pressure from the tank?

Is it reasonable to leave switching the system to mains for the bathroom fitter? How much work is involved how long would it take?

I feel like I am going to be oaying double for a job.

Any advice/help in this matter is greatly appreciated. Cheers