I have got an old potterton bolier providing DHW/CH via a cylinder and
header tanks. The boiler is an old cast iron one and is absolutely
fine but at some stage it will need replacing. The obvious thing to do
is replace like for like and continue with the system I have got. The
other option is to replace with a combination boiler and remove the
old cylinder and tanks to create extra space in the bathroom and loft.

I'm prepared to give this a go myself if the sequence of events is
logical. What considerations are there in converting from the old
system to combi boiler? The pipework will obviously change but not to
drastically. The pump is upstairs in bathroom. This will need to be
removed as new pump will be in combi downstairs. The cylinder and
header tanks will need to be removed and relevent pipework
reconnected. Will taps, cistern washers etc need uprating?

And finally if I do go down the combi route, what size/type would be
recommended for a 3bed 3reception house currently let out as a 5 bed
1recepion with 1 kitchen and 1 bathroom (with electric shower, which I
could convert to thermostatic).

Any help gratefully received

Charlie