Synergie MK1 gear cables

[Firemoth]

Just had a failure of my gear selector cable. Stuck in 3rd gear for 20 miles........ In Luxembourg on holiday. Not fun

Managed to bodge it for now and hopefully it holds till we're home on Sunday.

Has anyone replaced the cables in these before? I've done other cars and found them not difficult as such, but very fiddly and awkward.

Any hints and tips welcome

Thanks