Originally Posted by
JRat
Thank you for the advice and suggestions. However, as I'm in UK I've decided to first try what is available here so I've ordered a 2-piece front clamp unit (item B07T4KTZBD from Amazon UK) as it's both cheaper and quicker to get than something from Asia. If it becomes obvious that it won't work then I'll have to move to a more expensive solution. The photos with that product listing also illustrate your point about the cable routing from below - I had been thinking of the cable pulling from above which would be a straighter routing from the hole in the frame.
Most bikes factory equipped with a front derailleur use a cable+housing coming from the bottom and most front derailleur (I could even say almost all) are made for a cable+housing coming from the bottom.
My Birdy was factory equipped with a front derailleur and a 52-36 compact crankset and has its hole in the frame above the derailleur. Nevertheless, the cable+housing make a loop to the bottom so that they can come into the derailleur from the bottom.
I listed Ridea and Color+ which are high end expensive brands as examples but there are cheaper types from Litepro for instance available on Aliexpress.