Finally connected the 'temporary' external wire
Things happen slowly here. Very slowly... I finally got some coax fed out through and air brick and connected the external random wire up that slopes down to the workshop so I cna use it without needing to open the shack window and feed a cable out.
Experimenting, the tuner was happy on 6, 10 and 12 but less so on 15 with the rig seeing a SWR close to 3. It would tune 30m too but knocked the GPS signal to the clock off, clearly RF in the shack. I did not try lower because I then realised that, like a twit I forgot to fit the 1:1 unun!
With the 1:1 unun installed outside the tuner was happy-ish with 15 but now not 12. Oh well. And it refuses to get below a SWR of 3.0 on 30m and is quite bad on 40m which is annoying, but on the plus side tuning does not knock the GPS clock off! I suspect I have managed to get an awkward length of wire so I will shorten it later on and expreiment further. Surprisingly, it is happy on 80m and it will tune 160m but that did knock the GPS clock off and I am amazed the place isn't on fire! That was just a very quick experiment and I am under no illusions of the futility of such a short bit of wire on that band, or, indeed on 80m.
In any event my FT8 signals at 25W were picked up on various bands well across Europe and into the US and Canada with reports via pskreporter broadly similar to the loft long wire, although of course this is extremely subjective especially with compromised bits of wet string. But reports are reports.