kwik fit used to do a recharge for around 20-30 quid and if they didnt get it cooler then it was you didnt pay.
might be worth giving them a go.
do you have climate or just normal aircon?
if climate and it flashes for around 15 seconds this indicates there is a problem within the aircon in general,possibly low refrigerant?
if you apparently topped it up yourself and a few days later it disapered then there possible is a leak within your system somewhere.