Most chippy chips are fried in the same oil as the fish, so are contaminated.
Standard McCain oven chips are GF (and say so on the packet) - they have various other ones that have flour added which should be avoided. Potato waffles are also GF, if you need processed potato in some other shape!
There's loads of Free From stuff these days - the choice is really quite good, even if the implementation can be a bit hit and miss. Beware of the pizzas that have vegan cheese on them though - the bases are probably OK but heated vegan cheese is essentially napalm - it's hot liquid that won't set and sticks to and burns any body part it touches.
Brownies, biscuits, pancakes - basically anything that is sweet and solid can be really good. Anything that needs air in it (break, sponge cake) generally tends to either be a bit solid or a bit rubbery (they do stick it together with gum after all). Sadly, that means that if you want to eat baked goods, the only nice ones are really bad for you.
We've had a GF household for 9 years now (my wife is coeliac) - it's much easier and better than it used to be (my granddad was diagnosed in the early 90s and had to order specialist bread and pasta type stuff from a catalogue).