climate control

Hi All I have a 2005 octavia elegance (later shape). Took it in to the local Skoda dealer for a climate control re-gas. A month later the climate control failed so i took it back. They did another re-gas with a dye added. About a month after that it failed again so the dealer checked it out with- i believe a uv light. They could not find a leak and said the next job was to take the dashboard out which they said would be costly but no guarantee of repair was offered. I declined and have looked on the net. A company sells small canisters of a sealant kit which lubricates seals and they also sell cannisters of the refill gas. Has anyone used these type of repair kits or got any suggestions on repairing the leak. It must be a very slow one as it takes about a month for the climate control to stop working. Many thanks.R