Pressure issue with hot water - What is the best way to fix?

I don't think it is ideal to fit a pump to a fortec cylinder. A direct unvented cylinder will certainly give you the pressure you require. The tank in the loft will only give a small increase in water pressure, maybe an additional .2 bar.

hi Fortec cylinders are very low pressure systems which tend to be very problematic with today's taps and showers available on the market as most products will not function satisfactory. The fortec cylinders are not really suitable for pumping to boost the water pressure as the volume of cold water is too low and will run dry and damage the pump. The best solution for showering is to use an electric shower which is mains fed to avoid the issue with the shower head being higher than the cold water storage tank or go for the unvented option. More that happy to quote for the job For taps that work with fortec cylinders for best function choose seperate hot and cold taps, or mixers with 0.1 bar pressure rating. With mixers you will need to have non return valves fitted to the hot water supply which will slow down the flow even more, also in lots of mixing situations the cold pressure will stop the hot from flowing all together.

If you have a copper cylinder, just fit a 1.5 bar pump, for hot water only, sound proof it, should sort out problem, they retail out at about 150 plus fitting. Hope this helps