Impartial wheel advice please

My father-in-law has just passed away, and I'm trying to help my mother-in-law deal with some things.

I've picked this forum as there's normally plenty of debate about wheels and I'm looking for some honest and impartial advice.

He was a Mercedes-Benz man and only changed to a new E-Class in September which currently has just 3000 miles on it.  For his previous E-Class he bought a set of original 18" MB wheels and Dunlop winter tyres for about £2k.

The new car came with 17" wheels and I helped him get them changed over to the winters a couple of months ago.  I suspect that long term his plan was to ultimately use the 18" with summer tyres and put winters on the 17" which would have been sensible; but unlike the 17s, his winter set were of different sizes.  He had:

Fronts: 8.5x18 ET48 5 spoke MB wheels with 245/45 R 18 Dunlop SP Winter Sport 3D (6mm remaining)

Rears: 9x18 ET 54 as above with 265/35 R 18 Winter Sport 3D (5mm remaining).

The wheels have seen 1 winter and 5 trips this winter and are unmarked.

Any advice on a sensible price would be welcome as I'm trying to do the best for my mother-in-law.  As they're a different marque I thought you lot could give me some honest feedback.

I know there will be forums where I can advertise them but just want to get an idea of roughly where to pitch it so that no-one takes the p1$$ in the circumstances.  The fact that these are quite low profile and a niche winter size (as well as being different sizes) makes this tricky.

Thanks.