I have a boiler upstairs that feeds through the wall under the bath feeds the bath and basin then goes down to kitchen ..but the bath water is not as hot as the kitchen tap and I’d like my bath to be the same temp as the kitchen
That's normal in households with high mains water pressure. You have to fit stopcock on cold feed to the combi boiler and use it to reduce water flow through the boiler. If boiler is 24 or 28kW there's no chance it will heat fully open bath tap to 55C.
You may have a temperature restrictor valve on your pipework under the bath. This is now regulation to have them fitted to protect infants from scalding themselves. The valve can be adjusted to make the hot tap, hotter. Or quite simply be removed.
Not enough pressure going trough and to the 2 taps