Ok m8, have a go at this. Firstly give the underbonnet area and engine a good wash to get rid of any old evidence. Once its clean the best thing to do is simply to pop it into a regassing centre, not the VX stealers, prickfit or haflords though cos from experience they are far too expensive and not as good as they say they are, and the usual practice is that they de-gas it by vacuum then re-gas it and add a UV flourescing dye. They then run it until the aircon is working and then the test for leaks. Try NOT to use a place that uses the Electronic' sniffer though because they are unreliable and give many false alerts. Use a place that use the dye then searches for leaks with a UV lamp which makes the dye light up.
If they do discover a leak they will offer to do it for you but ask on this forum for a recommendation of a place near you that has been used by an oofer's before.
Remember, the mig is a funny car and not a lot know how to service their needs. many can talk the talk but very few can do the walk too.
Hope you have a cold blast soon,
bionic