Before you commit to ditching the existing boiler, some food for though here:
//www.diynot.com/forums/viewtopic.php?t=210139
Without seeing your cylinder its difficult to say what needs doing, but £1000 for a cylinder change does seem steep.
//www.diynot.com/forums/viewtopic.php?t=210139
Without seeing your cylinder its difficult to say what needs doing, but £1000 for a cylinder change does seem steep.