With on going industrial action on the railways, visitors might like to check out the following site to see which trains are running. Even in normal times, it is a useful site for giving updates on the progress of trains and if you click the actual train, you will usually see a photo of what type is on that service. Put your start point in the location box. If doing a day return - make sure that you can also get back. Note that things can change and you should also check the train company websites.
https://www.realtimetrains.co.uk/search/detailed/
Note that some of the trains in faint type are freight trains. Some trains that were originally scheduled may not show up as cancelled because they were already ‘removed’ once they knew that strike action was coming.
It looks like they are mainly targeting weekends to disrupt leisure travel. Brits who don’t have to travel are staying away so at least this frees up space for those with no alternative but to use the trains. Having said that, with many services not running, you can expect those that do to be very busy.
If planning to travel by train, best to avoid the weekends by the look of it. I would avoid Sunday travel by train at the best of times as this is the day when engineering work takes place more than other days. Another factor is that with many train companies, Sunday is not part of the working week and they have to ask for volunteers to work overtime. (This is one of the reasons for the dispute as train companies want Sundays to be part of the normal rostered week).