Before I have a gas safety inspection and potentially have it fail, does
anyone know..

(For a house we want to let)

The boiler flue (combi, not condensing I don't think) goes from the
boiler in the kitchen, up through the ceiling to the attic bedroom
above, and out through the roof.

In typing, I've just realised it must pass boxed-in through the
first-floor bedroom, which I presume I now have to install flippin
inspection hatches on?

In the attic bedroom, the flue just runs from floor to ceiling. Not
boxed in - just the metal flue pipework.

Is that bit allowed? Or will I have to box it in somehow? (If so,
there's going to be a follow-up question of can I do that myself, and
what rules/regs are involved?)

Cheers!