poor hot water flow

My daughter has moved into a flat with an A Class. Its takes about 4 minutes to fill up a bucket a water (OK slight exaggeration but not much) but the water pressure on the hot taps are nowhere near the same as that on the cold water. It is an extremely hard water area and reading the documents from the web it says the heat exchanger could need changing. But I am having difficulty in finding anyone in the Hemel Hempstead area who can really just pop in and tell me I really have got an issue and the A-Class needs fixing or that I have another issue. The best so far is Gledhill Response at £120 but even then I have to pay the full fixed service charge and they refund if they dont find an issue . Know anyone local to Hemel Hempstead?

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Mike