I like a good cheese and onion sandwich, but not like that. It all had to be shredded, only a bit of onion and mix it with mayo. I've never had a handmade one either, but got them from a supermarket, like M&S. I'd look at that roll on the OP and think of it as a pisstake.
We like cheese and we have really good domestic cheeses, as well as cheeses imported and inspired by Europe. I'm partial to cheddar, stronger the better.
Beans on a jacket potato? It's a thing, but not my favourite. I like baked beans but they have to be applied carefully, as they tend to overpower everything. On the side or not at all.
I've never heard of Tuna and Coleslaw. Seems like a baffling combination. Never seen it on a menu either.
I like tuna, but I don't like it hot. I won't eat a hot tuna and cheese panini even if it's given to me for free.
I generally don't eat jacket potatoes outside, as they're really easy to screw up. My favourite is to cover it with beef gravy, some pepper and have some grated cheese and tuna on the side, as not to mix or heat them too much. Delicious and haven't had it in years.
Another thing is that potatoes with beans and cheese and onion sandwiches tend to be budget meals. A cheese and onion sandwich, for example, will be on the cheaper end of the sandwich range in a supermarket.
