Yes, just came to that conclusion so have set up a shipping class in the UK Zone (so far) with a price specified for A5 and A2 plus A3 and A2 which I can then add to each product appropriately. I’ll test this tomorrow to see if it calculates everything as I’d expect. If it doesn’t then I’ll probably try the Advanced Shipping Packages extension.
It’s been a while since we heard back from you so I’m going to go on and mark this thread resolved. If you do have any questions, feel free to open up a new thread and we’ll go from there.