We will be upgrading the forum software Wednesday morning - the site may be down for a while during backup/install.
I agree with all the pro-insulation lobby above (or below). Just had my single skin brick garage insulated - studwork, Celotex and foil plasterboard over the top, chipboard floating floor / carpet tiles, plus new door and window, probably £2.5k all in, including labour, which was a bit less than half the total. I also invested in a proper (Meaco) dehumidifier - cost about £250 and I run it continuously for now as it's winter. It draws about 300W iirc, so I guess similar to a small computer server, but it's really effective with a humidity of 45-50% and it keeps all my cherished stock and electronics damp-free and rust-free! Prior to this the relative humidity was about 90%.