Solve our water pressure problem

We need a qualified CORGI plumber to solve our water-pressure problem; currently the problem is that the shower pressure is not adequate.

We have an old-style boiler (not combination) and there is very low pressure in the shower, most probably because the water tank is above the shower and there is a very small vertical distance between the tank and the showerhead.

We are thinking of either replacing with a combi-boiler (but prefer to avoid it as it will be expensive) or just install a simple shower pump for now (or open to any other solutions that you might have to propose).

Just for reference, there is good pressure on the cold water kitchen tap which suggests adequate mains water pressure.