Hello Sleepy, my reply is waiting for moderation.
Hello Grandy, this seems to be hard work but can save you money instead of buying new timber, so of the skirting boards may already have an angle cut at 45 degrees, you can use them for one wall if they're long enough and then you can buy a timber or plastic mitre box for only a few dollars, if you don't have an electric drop saw, a normal electric saw can cut 45 degrees but this can be rather awkward.
What I would do is place the already cut 45 degrees and place it in the cheap mitre box so you can get the feel of how to use the box for other walls and if you cut them yourself and they aren't a proper fit, then they can be filled with polyfilla and moulded into the right shape after you have nailed them to the wall, remember you can use water to mould them rather than using sandpaper, if that suits you.
When taking out a nail from the skirting board, place a spare piece of timber under the head of the hammer and between the skirting board, this will make it easier to pull the nail out and won't mark the board.
Hopefully, the boards will have 45 degrees for each corner as well as external corners, such as for a wall that's not for a corner of a bedroom, but for a wall that sticks out from a wall, hopefully you know what I mean.
Please mind your fingers and those nails you've polished, sorry.
My best thoughts.