Plant-based fish comes in a variety of styles. This page deals with the type of fish products that you'd use to recreate fish and chips, so you'll find fillets and also goujons on this page.
For the record, the best plant-based fish I ever tried was in a cafe in Brighton called The Loving Hut which was in an area called The Level. It was truly amazing, but sadly this branch closed down. There are other branches still open, but their fish options seem to be slightly different to what I tasted down in Brighton.
Gardein: Golden Fishless Fillets - ⭐⭐⭐⭐⭐
Frozen / 288g / Approx £4.50 (15.63 per kg)
Great batter, and the inside has a nice texture and flavour. It's the best plant-based fish I've had at home. The individual fillets are quite small, triangular-shaped (similar to a hash brown), so you'll probably need at least two.
Plant Pioneers: Battered Fishless Fillets - ⭐⭐⭐⭐⭐
Frozen / 2pk
This is a twin pack of battered fishless fillets. I wasn't expecting these to be as good as they were. The batter and the fish-like texture were both great. The have jackfruit in the recipe and I think this is key to giving these that great texture. They could benefit from a bit more of a fishy flavour, but it's not enough of a problem to remove any stars.
Finnebrogue Artisan: Naked with the splash! No Fish Goujons - ⭐⭐⭐☆☆
Chilled / 250g / Approx £3 (£12 per kg)
These were quite nice, but I did find the texture to be slightly mashed-potato-like.
Quorn: Fish fillets - ⭐⭐☆☆☆
Frozen / 2 pack / 200g / Approx £3 (£15 per kg)
The Quorn offering comes in two options; battered salt and vinegar, and breaded lemon and pepper. I remember being quite excited about these when I heard about them being released, however I found the fish part to be a tad on the dry side (I find all Quorn's vegan products have the same problem). Ultimately I felt a little disappointed with them and I haven't had them again.
Plant Kitchen: To-fish and chips (Marks and Spencers) - ⭐☆☆☆☆
Chilled / ready-meal for one /
The Marks and Spencers option is sold as a complete meal containing both the fish, the chips and some tartare sauce. The batter was really, really nice - possibly the best of all the products in this list. The biggest problem was, as you may have guessed from the name, that the fish part is just a block of tofu - it seems like there was no real effort to add some texture. Really disappointed, and even the amazing batter can't make up for this.
Since writing this I have discovered that M&S have introduced some battered fishless goujons, they sound better so I'll add them to the list once I've tried them.
Asda: Plant-based Fishless Goujons
MV Taste: Breaded Fish Fillets (Morrisons)
Plant Kitchen: Battered Fishless Goujons (M&S)