I got 500g for £5 from Wilko, which doesn’t sound a great deal but as you know they are incredibly light, so actually go a long way.
But I did see this: 5l volume for £13 sounds very cheap to me. There’s £2.99 postage, so would be £16 for 5l, but I think that still sounds very reasonable. I’ve not used them myself but I’d be tempted at that price.
Edit: it’s free shipping over £25, so for an extra £10 you could get two tubs, 10l.
https://www.chubbymealworms.co.uk/produ ... -mealworms