Upgrade without blowing a budget

[MajorStare]

Last month I had my 20+ year old Marin Eldridge Grade serviced after not being used for 18yrs. It really is in fantastic condition and I have been using it at the weekends to get fit. Usually involves a 40min ride with my 13yr old son, then when back home I go for another ride.
New clothing purchased, water bottle etc, so have all the gear apart from lights.
Terrain is woodland paths, dirt tracks, some steep climbs & decents and a couple of designated MTB tracks/routes.

I would like to sell the Marin (unsure on value) and get a newer bike. My budget is £1000 and I would like full suspension. I have pinned it down to Bossnut (can't get hold of) or a Vitus Mytheque (can't get hold of)
Have been trawling eBay but current lock down limits travelling to get a bike if i see one.

There is a Carrera Titan X not far from me, well in budget and gives me a few £ for some lights........ https://www.ebay.co.uk/itm/Carrera-Titan-X-Full-Su...

Another option (I would have to pay courier) is this one......... https://www.ebay.co.uk/itm/Jamis-Dakar-2021-Full-S...

Finally, this is just 15min from me........ https://www.ebay.co.uk/itm/CUBE-Stereo-120-Pro-Ful...

Interested to hear your thoughts on these or any others.