Moving a hot water cylinder

[Labracadabra]

Has anyone done this and how difficult and costly was it? The house we're thinking of buying currently has the cylinder housed in a cupboard in the master bedroom, but if we built an extension it would need to be moved to allow us to create a new hallway/corridor. I'm not sure whether we'd want to move it into the loft or to another spot in the house. Any advice? Thanks.

when we did our extension we removed all plumbing from the old part of the house into the new
and made all of the hot water mains pressure (no roof tank and easy mixer taps)
had no hot water for a while during !!
new tank is in its own cupboard topped with drying racks for towels and bedlinen