I think the PKU coolers are the only adult formula in the UK which actually have omega 3 in the formula itself (in the form of DHA, i.e. fish oils). Otherwise you have to take a separate supplement – the Docomega already mentioned. PKU Coolers come in 10, 15 and 20g protein pouches – I believe the 20g pouches are suitable for adults. I am trying to get my 3 year old to take the PKU Cooler 10 pouches but she isn't too keen! The flavour is quite strong and she is used to unflavoured formula. PKU coolers are made by vitaflo.
I add flax oil and fish oils to her bottle before bed. I tried the flax oil off the spoon and it tastes ok, I managed the whole spoon without it tasting too disgusting. I think it wold be nicer as a salad dressing though, maybe mixed with some olive oil and lemon juice. Flax oil contains a good balance of omega 3 / 6/ 9 but it does not contain DHA (what you get from fish oils) – I think it contains AHA which the body then has to convert to DHA – but don't quote me on that I am definitely not a dietician! So it is good to have that AND fish oils, I believe, as fish oil contains the finished DHA oils. I also add flax oil in baking – I use it in her fate pancakes (50:50 flax oil and sunflower oil) and it gives a nice nutty taste, but burns a little more quickly than usual.
The eye q fish oil liquids (vanilla and citrus flavours) taste ok and because they are liquids do not have a gelatine capsule so are Phe free. You can buy them in most chemists (Boots etc). I add the vanilla flavour to my daughter's bed time bottle – obviously not appropriate for you but perhaps you could just take it off the spoon or mix into some cereal etc? It is quite expensive but I do this because my daughter is very resistant to changing her formula, which she loves and I don't want to rock the boat! However, I might ask about the Doc omegas at our next appointment as I would rather get something on prescription if possible.