With the vast majority of new builds I've been involved with sorting out, the housebuilder doesn't connect anything at the other ends of the cables. There's no TV aerial, no distribution amps, nothing. If you go in the loft, the wiring tails come up at various points in the space. They're not even grouped together. When I've installed gear then, I've also had to extend the cables so that they'd all come back to a central point.
Unless you've bought (and paid for) a third-party installation company to come in and pre-wire then install distribution gear, then I strongly suspect you're in the same boat as above. To put is a different way, you'd remember being sold the TV distribution package, and there should be a manual from the installation company that details the gear and its capabilities and the all-important service number so that they can soak you for aftersales support fees on your 'bespoke' installation.
What you've got in the various rooms is grid module (A.K.A. Euro module) wall plates with individual connections. That means there should be three aerial/satellite cables along with an Ethernet cable for the network jack.
I'm keeping my fingers crossed for you that your TV and satellite modules are shielded. Cheap ones aren't, and that causes problems with interference. Shielded connections have what amounts to a metal can covering the bare wire connection. Unshielded ones have a simple circuit board with screw-down connections but no cover.
You'll be able to check what you've got either by levering out one of the modules with a flat blade knife or by unscrewing the frame.
Your installer for Sky will be on a time-limited schedule. If he's a Sky employee then he'll have to stick to their rules about where he can and can't go. This includes restrictions about working at the sort of heights required to get cables up to roof height to enter through the eves, and them not being allowed to go in to areas such as lofts. Since you're getting the installation 'free' or virtually free/substantially discounted then it's difficult to argue with their policy, and they wouldn't change it even if you did. The eves work may change if your property is a bungalow, but the loft work is nearly always a difficult area.
Sky also uses subcontractors for installations. They're on an even tighter schedule because they have no fixed wage. They only get paid the contract rates for pre-agreed work. They may be more open to having a discussion about making better use of your wall sockets, but I would expect there to be a cost involved if they agreed.
An alternative for you is to contact one of the local aerial installation companies to come in and sort out your system prior to Sky's arrival. This would cover discussing the options for various solutions ranging from just a basic aerial installation with simple passive or amplified splitter through to something more comprehensive such as a Sky Q compatible multiswitch to make all of the house satellite sockets live (for Freesat as well as Freeview) and telling you what you need to discuss with Sky prior to your install date to get a hybrid LNB.
The work an independent would do would include the onerous task of tracing out the wall panel connections back to the loft. Don't underestimate the time and effort this will take. Even with some of the tools we use it may take a chunk of time and involve lifting boards in the loft if some of the cables has been buried. Another thief of time is putting right any problems that the electricians and other trades caused during the build.
(TL; DR) - Don't assume that Sky's installers will have time to faff around trying to work out what you've got. They're more likely to put the dish up off a short ladder, then run the cable a short distance before drilling the wall close to the main box position.
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