Hard to pinpoint the causes remotely. Think the car needs to go back to whoever did the work because from your description, it appears no better and still shows the same symptoms.

Could be a number of things. Ist thing comes to mind, was the cooling system correctly flushed and bled ( very important ) after the work? Secondly, was the work REALLY necessary in the first place. It would not be the first Rover to have a new cylinder head gasket fitted which did not need it.

Regarding this and other things you mention, seek out someone who has a good knowledge of these cars and get their opinion. From what you say, appears that the car is in need of some TLC .... Maybe someone on this site lives nearby and can have a looksee... whereabouts is the car.

How much did the work and new radiator cost? Was it done on the cheap?
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Airlock perhaps? While you are at it and for the sake of £6 buy a new coolant tank cap, some of the older black ones can lose their seal over time and that can cause overheating.

I had similar symptoms after my HG was done, and that seemed to fix it, as well as a good flush...

 

Thanks- I'll tell her to go back to where it was done, based on what i've read about head gasket failures, and after checking the car for what I read about i didnt think it really needed a head gasket, but im no expert to say the least!

the work was done for about £350 i think, but i'll double check and see exactly what she's had done. Just ordered her a new tank cap (got one for myself too(!)) so i'll try that, and we'll look at flushing it out when i can or ill tell her to get the place that did the work to do it.. in the meantime, any other possible suggestions? Just to check, would it be simple enough for me to bleed it myself if i read into it?

cheers

 

Sounds like inlet manifold gasket.Change it anyway if car is oldish. Hope this helps