What type of shower can i use next to a combi boiler? ...
You stipulation to use a thermostatically controlled or mains pressure floating shower.
Are you referring to the shower mixing stopcock. Manufacturers and plumbers merchants will tell you which ones are suitable.. As the hot hose down will be mains pressure it is best if you nurture the shower with D cold water as powerfully. This leads to hanging pressures on either side of the mixing tap.
With reference to previous answer.
Although an electric shower will make a contribution you back up if the combi boiler go wrong you will get much better flow rates and thus a much better shower if you use the combi boiler.
Answers: How about going for an electric shower which wouldn't affect your combi boiler ?