Is new heated towel rail causing combi boiler water heating trouble?

[KerrieRankin]

I have recently had a new bathroom fitted - including a heated towel rail. Since then we have had problems with the hot water in the upstairs of our house. Gets hot, then cools off to luke warm, or goes completely cold as the boiler has stopped heating the water. We have had a boiler man 'service' the three year old boiler and give us a clean bill of health, but we are still having issues. Could this be caused by an airlock or faulty removal/installation of the rads? Our pressures are correct and I can't think of what else could be causing the problem?
Thanks in advance for any responses. I am in the Westcliff on Sea area if anyone can recommend a good boilerman.
K

[boxtops]

I wouldn't have thought so - we have a combi boiler and a heated towel rail, and our guest bathroom is two floors up from the boiler. I'd change your service arrangements, either your boiler's duff or you have an air lock, IMO. Our hot water is ready on tap whenever we need it. Have a look in your yellow pages, or ask your neighbours - personal recommendation can be a good thing.

[AlBags]

I assume you mean a 'water heated' towel rail?
You can get either electric, water or even both combined.

Hot Water upstairs is un-related.

What happens if you turn down the flow .. does it stay hot?