does installing an unvented cylinder, make any improvement to water pressure or volume?

It all depends on the pressure of the incoming main to your property, and the size of your boiler? If the incoming main is low pressure then, unfortunately there’s not much you can do, unless you fit a pump? If the incoming main is high pressure, and your boiler is a low kw output, then that could have an affect on the pressure also!! Fitting an unvented hot water cylinder would increase the hot water pressure but not the mains water? Thanks.

no.your pressure is governed by incoming main pressure,fitting an unvented cylinder will not increase the pressure.

Best way is to contact the water board and tell them the water pressure is low They will come out free of charge and advise you on the pressure you have When fitting a COMBI I always test the incoming water supply because sometimes the pressure is too low to install a COMBI so a regular or system boiler would be more appropriate and a pump for the shower

All previous answers are spot on, all comes down to water pressure from incoming mains,