We have just moved in to a new house with a Galaxy Alarm with a MK7 system
The MK7 is just the keypad model number. The actual alarm will be something like Galaxy 8 or something - does it say anything on the control panel cover? Bear in mind the alarm might go off if you remove the panel cover tho.
I inherited an old ADT Galaxy 8 alarm with a house move and changed the panel to a more up-to-date Galaxy panel. New Galaxy G2-12 panels (12 zone) are on ebay for about £30 and would probably be a straight swap. You'd possibly need a new battery at another £20 or so if yours is old, and possibly a new battery for your siren.
It's not too difficult to swap the panel over if you're confident, but the installation manual takes a bit of getting your head round. Most of the alarm works by 12 volt dc, so it isn't that dangerous. Obviously it's powered by 240 volt mains tho so if you're not confident get a pro in.
Some side notes:
You can get an ethernet module for the Galaxy if you wish (£50), which gives you full control of the panel by phone app or internet etc, and it gives you texts/emails/calls if the alarm goes off - for one quid per month. Google "selfmon" for more info, a few others on here also use the service. (I've no affiliation to the company other than being a happy customer).
The MK7 keypad is also available with "keyprox". These are small keyring tags which you swipe against the keypad for setting and unsetting. The keypads are a bit more expensive (but look exactly the same and would be a straight swap) and are great when you return home with hands full of shopping bags etc.
Some MK7's also have volume control which we find invaluable cos we come and go in the middle of the night due to working shifts, so it's not so noisy pressing buttons.
The Galaxy (and probably other alarms) has a night setting where you can programme whichever sensors you wish to be active while you sleep, and have other zones inactive.
