my outlet pipe is about 10 foot long and runs out of a bedroom I would need to go up a ladder to see to mine!
What diameter is it?
You may not need to do anything, the problem is a slow trickle of condensate gradually freezing and blocking the pipe.
The first condensing boilers are the worst, they just let the water trickle out, also large enough diameter drain pipes were not fitted.
Then siphons were were fitted in the boilers to stop the trickle and cause rushes of condensate from time to time, larger diameter drains were fitted.
Depending on the installation some installers go one step further and fit a reservoir and pump to further increase the volume of condensate discharged at any time.
The build up of ice usually starts at the outlet where residual drips form, placing the outlet in a gully slows this process down, having the end of the pipe under water in the gully virtually stops it.
If the end of the pipe is exposed you can feel to see whether ice is forming and if it is pour hot, not boiling, water over it. Boiling water can damage the pipe.
If you feel like a boring read
Current HHIC Guidance
https://www.logic4training.co.uk/wp...TE-DRAINAGE-PIPE-INSTALLATION-Final-20111.pdf