They are still operatives of British Gas and working on their behalf so that's no excuse.
It's obvious that the installer patched the condensate pipe connection with a sealant, more than likely silicone. A proper condensate tee connection to the waste is required and any installer that values their reputation and cares for their customer's property would have fitted one at the outset.
Doodlebug, it's admirable that you are wanting to address this complaint, but in my opinion, you should stick to your own back yard before a flood gate of customers complaints land on your doorstep via this forum.
Up here, Scottish Gas are not too bad, except for their heavy handed sales tactics for items that are not needing replaced.