Glowworm Majorca three Problems Help Req?

Hello there,

My Mother has an old Majorca 3 system but does not have the money to replace it at the moment so I was wondering if someone could help.

When she switches the heating on after a short while it will just go off.. Is this a problem with the thermostat?

She can't have the thermostat on too hot either because the hot water comes out scalding.

Where abouts is the pump located if I need to check this?

I know she should get a new system but funds are just not there at the mo but out of interest how much would it cost to change/replace system.

all help appreciated so thanks in advance.