Upgrade advice

[malaxim]

I'm about to upgrade my standard, 15 year old gas boiler and would like to take the opportunity to upgrade the system to allow me to put radiators into the 3 bedrooms on the third floor (7 bedrooms in all) and add another shower unit to the biggest bedroom, giving me one in bathroom, one in bedroom.
The present central heating is pressurised but the water is normal. Its been suggested I change to a fully press system and lose the cold water tanks, etc, but isn't this dangerous.
I know I'll need a larger and different hot water cylinder, more expensive no doubt too, and I can't use a combi boiler if the system is unvented. Are there alternative boilers that meet the new regs?

 

[fitz1]

potterton powermax 150.All in one boiler and cyl. Pressurised system . 3 bar hot water pressure. 48 litres per minute.

 

[bab]

If u get a good installer no problem. Crossing the roads dangerous to. personally id go for the mins fed hot water cylinder with seperate heating boiler if you r thinkin long term. repairs on seperate items work out less in the long run. Also gives u more flexibility with ya type of capacity.