How do I improve hot water pressure from a gas combination boiler?
I'm in the UK, we got a new recently due to the rebate recently offered on really old boilers.  

If you get a decent boiler it provides savings because it is more efficient. They are called "condensing" combination boilers - the condensing action reclaims lost heat, I think.

We got a Vaillant, who also make the glow-worms.  Never heard of Ferroli.  And yes we get decent hot water pressure. I would check with a few plumbers/gas engineers, just get a few quotes, and also check the boiler specification for max flow rate.

Couple of tips if you do get a new boiler be sure to specify exactly where the pipes go (if you change location), get one of the remote controls (very handy, and allows you to put boiler in loft), and also specify exactly how you want the magnaclean device fitted (collects sludge from central heating). Ours is unfortunately very prominent - we need to move it.

Also, we went for a really big powerful boiler, so more than enough water but tbh probably a bit too big for our house: bigger may not necessarily always be better.

I'd only get vaillant, glowworm, or worcester-bosch, btw.