Heat Exchanger problem with Glow Worm 30ci

[Wagonwheel]

I have a 7 year old Glow Worm 30ci and I'm experiencing problems with hot water flow - basically have to turn the taps down to a trickle to get hot water. The colder the temperature outside, the worse it is. I've been advised that my heat exchanger probably needs replacing.
Would this be down to limescale (I live in a hard water area) or is it just wear and tear? If limescale, my insurance might not pay out and I can't afford to replace it otherwise..!

I would be grateful for any advice. Thanks.

 

[glasgowgas]

take it you are refering to plate heat exchanger

this is the seperate heat ex primarily for hot water

you remove it, use a de scaling solution , and refit