Transmission1

I'm getting ... on 433.1750 MHz

Anyone know what that is?

It's kinda intermittent, so if you want to hear it, you'll need to be patient. I've tried to pin down any pattern to the TX times, but there's none that I can determine, save for it seems to repeat apx 10 to 15 minutes between transmissions (e.g: 10:07 then 10:12 and 15:00 then 15:16, but this does vary, from day to day).

Probably an error in your CW as it will almost certainly be:
GB3TS (--. -... ...-- - ...)

The repeater isn't very far from you

Thank you, milly.

It's real hard for me to catch. I've also heard 'voice' on that freq, which adds to the challenge.

You know it's in part of the spectrum allocated to radio amateurs. As Good Buddies Limited want people to use specific bits of that for specific things you can expect it to be a repeater output.
Clues like the signal strength being fairly consistent, voice as well as a CW ident makes it easier?