If you still have a local private chemist in your area it may be worth asking. I got a load of 2.5 liter ones virtually given to me when I lived in Barnstaple.
I agree with Neil, try your local chemist. I suspect you can still buy them but they are probably expensive. Its better anyway to store the chemicals in smaller volumes, they will keep longer.
Peter: thanks for the link, I even did not know wat Winchesters were until I saw one....
I kept my liquid chem's in 1L green whine/port bottles with a srew cap and labled propperly.
Worked for years untill I moved to a diferent place without a darkroom.
Any colloured 1L bottle with a srew cap would do I guess and it is cheap.
In the North West of England Boots the Chemists seem to be presently buying out all the local independent chemists, which was agreat boon to me as I've just got my hands on two 2.5L and two 1L Winchester bottles for nothing as part of a clear out/refit. Worth keeping your eyes open!
It looks as though the 2.5 litre size Winchester bottles are the largest that are commonly available. The 5 litre size demijohns might be suitable, provided they can be made air tight. I might also check around the local chemist stores as suggested.
Thanks to everyone who replied.
When I worked in a pharmacy, we routinely discarded the 2.5 litre 'Winchesters' that in which cough linctus was supplied in bulk, and most pharmacies get through a LOT of cough linctus. You'd be doing them a favour by taking the bottles off their hands.
My wife works in a Hospital Pharmacy. They regularly use and discard 2.5 litre brown glass bottles. She says that most bought-in products are now pre-packed in sizes for immediate use.
They have wider tops than Winchesters & are made by Fisher Chemicals. They seem to be the D'sBs, I'm really pleased with them. However, I think 2.5L is the biggest size. I too have had little luck sourcing Winchesters of any size larger than 500ml in the UK since Nigel Dear at Retrophotographic seems to have stopped supplying them.