Thanks for the info Jon. I bought some Prescysol EF to try and developed my first film in it at the weekend. Unfortunately the film had been used in misty, frosty conditions where contrast was minimal and the Delta 400 developed in Prescysol EF created extremely low contrast negatives when developed for 10.5 minutes. Should I have developed for longer or would this have made little difference with this developer? I've posted a lith print made of one of the frames to the gallery so you can take a look!