Hi Marky,
You can get a range of different key cabinets and key boxes, you can have outside ones and inside ones, the outside ones generally hold 1 key in which you wall mount and have a combination to enter so that you can gain access (this is best suited to social services and emergency services, to gain access to vulnerable peoples homes.)
other key boxes would most likely start at 10 keys (which would most likely be ideal for you) going upto the thousands.
I think Fast Key Services sell key cabinets at very good prices, go check them out. Media URL: http://www.fastkeys.co.uk/key-cabinets
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