Is it worth getting air con for a loft and properly fitted or portable?

[Alloutofusernames1]

Any experiences of this? I am getting a loft conversion and want to make sure it isn't going to be boiling hot. Specific questions:

Can the portable units' pipes be used with a Velux? Does the pipe stay in place?

Are they enough if you use them for a couple of hours before bed because you don't want to sleep with them on overnight?

Or is it better to fit the full blown proper units at this stage (but £2000 a unit it seems).

We have a portable unit that comes with an extendable hose. It would probably just about reach a velux window. We turn it on an hour before we go to bed and it cools the room sufficiently in that time. We would love a built-in one as they're much quieter and the room heats up again overnight, but can't justify the expense at the moment.

I was planning on having underfloor heating in the loft. Out builder said no need as it will be quite warm anyway. Didn't believe him at first but sounds as though he may be right 🤔