A photo would help2.4m, installation area is a bit funny. It's currently the corner of our kitchen but will become a utility room next year so we're not worried about short term awkwardness (want to do it now to make the loft conversion easier and so we can remove airing cupboard and do some more work there over the winter). But there's also a window on the wall perpendicular to the wall the boiler is on, about 400 in off the top of my head
If you do go for a separate boiler and cylinder, the Joule High Gain will give you super-fast reheat times when piped for hot water priority, so you don't need such a big one...although the 200L is only 1.15m high which should give you plenty of room above for a boiler and lots of storage too.