Advice on replacing Boilermate II and Potterton Suprima 18 yrs old

[Confused.com]

I have a Boilermate II under the stairs (in the kitchen) and a Potterton Suprima gas boiler in the kitchen and am impressed they have lasted about 18 yrs even though I live in a very hard water area! I have had a service contract with British Gas and for many years they have serviced it annually, and where necessary repaired these items with several PCB boards, Pump etc etc. But last time BG came out to fix the system they said it was time to start thinking about a new boiler and possibly tank. The CH control is in the cupboard on the Bm II tank under the stairs (nightmare to access) and has not worked properly for years, so I have the hot water and heating on 24/7 and control it using the thermostat in the living room. Not ideal, and I am aware this may be costing me extra on my heating bills.
I am a total novice and have been given various conflicting advice by BG and other CH suppliers - one said don't bother replacing Boilermate II if it is working ok, but I wanted a Worcester Bosch boiler as I hear these are the best and he said this is not compatible with a Boilermate II?
BG said it is best to replace the Bm II as it is so old and will need replacing at some point anyway and cheaper to do it all at once (sounds sensible?) but at a cost of £1800!
My house is 3 bed / 2 bathroom and in the mornings there are often 2 people showering at the same time. I want copious amounts of hot water that will be delivered fast. My cold water feed from the mains is very powerful. New CH controls and thermostat will be needed outside of the cupboard under the stairs.
Any advice / suggestions as to what system to go for would be much appreciated. (from what I have read/heard a combi boiler would not be suitable for my requirements?)
Many thanks
Helen

 

[Dan Robinson]

I wanted a Worcester Bosch boiler as I hear these are the best

You've heard its the best, but have no idea if it is or not?

 

[simond]

£1800 to replace a BoilerMate and a boiler is too cheap. I think you have misunderstood.

If you want similar flow rates to what you have now an unvented cylinder and a boiler is a good alternative, if you get a Worcester boiler and cylinder there is a 10yr warranty offer on at the moment......but not via BG plc.