PUFAs and GC bought compost.

@Allex50 , I forgot to say earlier, from your description of your Allotment soil it sounds like clay based. Highly probable as many plots are. Although it has its challenges one advantage of clay is that it's naturally fertile so may not require so many inputs as other soils. That said Allotments have been and are heavily used and cropped so nutrients do get used up. Another product you can think about as well as your own compost is Rock dust or Remin, these are crushed volcanic rock, they help remineralise soils stimulate natural bacteria etc. Given it's origins, far less likely to be contaminated with any modern chemicals. I use this on my clay soil and it makes a tremendous difference, especially to long standing crops such as fruit (bushes &trees) but also to things like brassicas. Combined with seaweed products (probably not entirely PFA free as the Oceans are contaminated) and homemade compost all works for me.
As @NigelJ has already said PFAs are so prevalent now it's impossible to avoid them completely, but you can minimise your exposure.

Yes. I see B&Q sells it at £22 (NPK 0-0-0! Pee in it = 11-1-2 is that better?). I might indulge in an experimental way. With all this contamination debate I think I'll stick without buying in a lot of fertiliser next year as I have now a reasonable amount of compost to which I have now added 4 bags of leaves I've collected from the road. I've put down suppressing cardboard but expect that has contaminants! Wherever I tread, the veg I having fed, there is this dread, some b... wants me dead!