Dead central heating system

My system has an outdoor oil boiler with 2 pumps.

One goes to the downstairs radiators and the other goes to the upstairs hot water tank.

In the fairly recent past this pump also fed the upstairs radiators (no more)

A couple of years back the pipes under the upstairs floorboards had to be replaced and the 4 pipes could only be replaced with 2 ( they feed the hot water tank)

This is a very old system and my plumber is very reluctant to fix the upstairs radiators (or even to keep in touch - well there has been Covid and also he is getting on) and suggests that I don't really need them.

If I want to get them back in operation does it sound feasible to connect up the pipes that feed the hot water tank to the upstairs radiators (probably installing a new pump?)

Or is it possible that my plumber is right and could it be too complicated and unnecessary to undertake the project?

Why were the radiator pipes removed?

How many rads are there in the upstairs and downstairs loops?

It sounds like the best solution is to come off the hot water tank pipes and install a 3 port valve, so that the heating is seperate to the hot water.

You will have to have a thermostat and programmer for upstairs and a programmable thermostat for down stairs.

Thanks for your help.

It's a big house . There are about 10 radiators upstairs and downstairs.

The pipes were very old and rusty and so we replaced the whole length from boiler to the upstairs bot water tank (with narrower gauge flexible piping instead of the old 2 inch diameter stuff -at least I would estimate it at 2 inch).

There are two pumps at the boiler and one thermostat which I think must affect both the hot water and the downstairs radiators.