Best shower for low water flow?

[Pannacotta]

I'm doing up a family bathroom which needs to look good and be done on a tight budget.
The heating system here is pressurised but the water flow rate is poor due to old, narrow lead mains pipe which can't be altered on my budget.

One fitter suggested the Mira Excel, another suggested an electric shower. The boys often want a shower at odd times such as after football etc, so an electric shower would be convenient, just wondering if the new models are more powerful?
This one gets good reviews as does the Mira Sport
www.plumbworld.co.uk/aqualisa-quartz-105kw-electric-3283-20141

Any advice would be great, thanks....