Mick,have a look at the compressors at Machine Mart,they are based in the UK and have branches in many major towns and cities.A friend of mine got a compressor from here and it is excellent.The first one and the second one on this link will do more than you ever need for model use.They are slightly more than your budget but not much.Also don't look on the purchase of a compressor as an expense.Sure there is the initial outlay of money but your modeling experience will be so much better with the addition of a reliable air source which,treated well,will last several years.You will save money as you won't be needing all those air cans anymore.I used to use the cans and I would never revert back to them now.Best regards.
http://www.machinemart.co.uk/ranges.asp?g=102&r=2008