Bolier Mate A Class - OV Limited Hot Water

My bolier mate gives me limited hot water despite having the hot water on constant. I have British Gas cover and they advised that it was just the type of boiler owing to having no water tank the water has to heat through the pipes as and when required. Surely this cannot be the case, I can not even fill the kitchen sink far less the bath - is this a common fault does anyone please have a solution?

Hi

Before i start, i'm no engineer but i have the same system and my hot water is absolutely fine - wish my CH was the same.

This could be a fauly heat exchanger - mayve want to metion this to the British Gas guy.