[ainarssems]

That's a great idea to re-fill at A8Parts if you are going to the annual meat or if you are close by anyway as you can be sure they are familiar with the car.

You can buy DIY refill kits but I would not bother. I had one that was given to me by a friend. He bought it because his AC was not working so he thought he needed to refill it but it turned out it was faulty pressure sensor. I think it cost £40 for the can and £10 for the filler nozzle which is not that good value when you can get service at garage or mobile aircon man starting from £35 depending on garage and location. They do state on the can that it is good for up to 3 re-fills but there is 450g of gas in can and car systems contain somewhere between 400g on newer cars and up to 1000g on older cars so you could potentially need 2 cans on almost empty older car. Also they do have oil added in cans and you need to shake it during filling but I guess if you use it several times you will not get uniform mix at all times so could be adding too much or too little oil. And the only way to check fill state is by the pressure indicated on the gauge while filling on the low pressure side with engine running. But the pressure will vary a lot depending on temperature and not sure how reliable this method would be on newer cars that use constantly running compressor with variable pressure valve instead of older clutch switched compressor. And if you think you can can keep it and use later forget about it, the kit I was given was about 90% full when I got it but when I wanted to used it 4 years later all the gas had escaped from the can.

Proper garage kit will use vacuum to evacuate system, hold vacuum to check for leaks and then fill system with the correct amount of gas and oil using weight in grams instead of pressure to check amount. It will also filter and dry the old gas for re-use.