So, with the hot weather we're having, our old Golf is struggling to get cool inside so rather than pay £60+ for a top up, I decided to take a chance and DIY it. We've had the Golf 8 years and it’s never been topped up. Went to Halfords and bought a bottle of gas and a trigger and digital gauge which came to £72 with my trade card. Would have cost £90 without. Cheaper gauges and gas cans are available if you shop around and are prepared to wait for delivery. Anyway, I came out of the store, connected it all up, followed the instructions on the gauge and I was on my way less than 10 minutes later with the car blowing nice cool air. I used approximately one third of the bottle of gas, so still have enough for another couple of top ups.