No Hot water first thing in a morning?

Hi, I have a Glow-worm Swiftflow 80. We have had one of the valuves changed as water was coming out of pipe outside of house. Pressure kept dropping and having spoken to a neighbour who has been told the boiler is on its way out so to just keep topping it up and another plumber telling me we have a leak, I switched off the central heating in case there was a leak on the radiators and topped the system back up. The pressure hasn't since dropped, however first thing in a morning (6.30am when I get up) I cannot get hot water upstairs and its hit and miss whether I can get it downstairs, however an hour later when my boyfriend uses the bathroom he has no problem obtaining hot water. Any advice as its really getting to me?