I sympathise with you about the complexity of the issue. For anyone who is unsure, I suggest they go to http://www.defra.gov.uk/animalh/id-move/pigs/pdf/new_owner_guide.pdf which can be simply printed off and is a useful guide for anyone to keep handy.
Basically it says that anything that comes out of a kitchen, domestic or commercial, cannot be fed to pigs so in order to be able to feed potato peelings, you would need to sit and peel them somewhere other than the kitchen.
The complications arise when you come to the small number of exceptions, and this was better addressed, in my opinion, in the earlier version of this document which is no longer available. Milk is straight forward if it comes from your farm.
The second exception ‘Former foodstuffs other than catering waste food from kitchens etc (see above) containing rennet, melted fat, milk or eggs but where these materials are not the main ingredient’ leaves some doubt as to interpretation. The explanation in the earlier version gave you ‘e.g. biscuits, bread, cakes, chocolate, pastry, sweets etc.’ and arising from ‘bakeries, distributors, processing and packing plants, retail outlets, but only where meat is not used or handled or where strict HACCP procedures are in place.’
Personally, I would suggest that pig keepers maintain a strict code that nothing that has been in their kitchen or anyone else’s may go anywhere near the pigs. Vegetable waste straight from the garden is fine. Vegetable wast from a greengocer ditto but not if it is a farm shop also selling meat or even pork pies.
If you do want to look at the exception and source waste from a bakery, make sure that there is no possible cross contamination from pies containing meat, pizzas, sausage rolls etc. IF IN DOUBT, walk away from it and stick to properly prepared pig food sourced from a feed merchant.
I hope this helps
PS Chloe – I know Defra don’t rule in Scotland but I believe that the rules apply across the UK.