Installing an unvented system with a conventional boiler

[confusedbyitall]

We currently have a conventional Glowworm 120B Hideaway boiler installed in 2001, including grundfos pumps and a Drayton Tempus 7 electronic programmer. We want to install a new bathroom including a bath, shower, toilet and basin, convert the current small bathroom into an on-suite shower room including a basin and toilet and to have another basic toilet and basin on the second floor.

We have been advised to change to an unvented system in order to gaurantee good pressure; however, no one we've spoken to so far seems sure about whether we can use our current boiler with an unvented system such as a Megaflow 250ltr. At this stage we can't afford to change the boiler, what if any additions do we need to make to the boiler to accomodate the unvented cylinders?

We would really appreciate any advice.

[temps]

Hi
Any boiler with the correct valves will work on an unvented cylinder. Its only the cylinder that is pressurised, the heating water from the boiler will be ok on a vented central heating system with an expansion tank.

)