Almost no trains operated by Cross Country Trains are expected to run today and on New Years Eve due to a strike. These include trains in England and Scotland.
I don't know of any Cross Country routes in Wales.
If you are travelling by train in the UK this week or next you are advised to check before travel. In addition to this strike, most of the other railway companies are cancelling many trains because they don't have the staff to run the trains due to sickness related to Covid.