Ok I had a bit of a scan on Angling Auctions (angling-auctions.co.uk) & Mullocks (mullocksauctions.co.uk) and I could see some on previous auctions catalogues. A pair of Kingfishers at £90, 16 silk lines from 2 up to 6 for £150-£200

and various reels with silk lines on them. I think I remember seeing an unused original Phoenix (Buxton), but it didn't go cheap.
I think the days of getting a cheap silk line to refurbish may be over, as silk is back in vogue, especially in the US. They may be some cheapies on the Bay, but as my friend BlueOne found, they may be shorter than the originals, or may have some rotting/fungus which may be untreatable.
Terenzios at £90 or one of those French half lengths may be the best and safest way to go.
Cheers