Buying Train Tickets?

First, you don't see the dynamic pricing or rapid price changes common to US airlines with regard to train ticket. There are dsicount tickets available but quantity limited to specifically trains. In order words, the 7 am train could have a hundred discount tickets but only 50 available for the 10 am train. And once sold, they are gone for that train that day and hour.

The British train system tends to be the most expensive train system in Europe so it is more beneficial to purchase early discount tickets (if available). Discount tickets generally non refundable and non-changeable. So if you are locked into your time and schedule then try to buy your tickets especially if discount tickets are available. Trains rarely sell out so don't worry about that.

You can see demand-pricing in action on the NationalRail.co.uk website. Check each of your planned rail trips for the day you expect to travel. Note the fares for a few trains at times convenient to you, paying attention to the total travel time as well. Now check fares on the same trains for travel tomorrow. You may see some really large differences. That's a clue as to how much you might save by buying your tickets now. But the tickets will be for the specific date and time you chose, so you need to be quite sure the trip will come off on schedule.

Often you can even save a worthwhile amount of money by simply buying your tickets the day before you travel.

This all depends on the date/time/route involved.

Also be aware that as of this writing, there will be a train strike on May 12 & 13 that might affect your plans.

Thank you for the replies. I didn't know about the train strike! We're supposed to be travelling from Bath to London on May 13th. I will not cross a picket line. What is the most sensible alternative to the train?

If you are travelling from Oxford to London on May 13th the neat alternative is to take the Oxford Tube inter city coach service.

Either pre-book it or just turn up on the day. Your choice.

The train strikes on May 12 and May 13 are two different strikes- that on May 12 is by ASLEF- the drivers, and on May 13 by RMT (the train conductors). The former is likely to be the more disruptive.
In any event what no-one has told you is that your journey to Bath (and to London, if by train) would be disrupted by the bridge repairs south of Oxford.
It is rail replacement bus from Oxford to Didcot then train Didcot to Bath.
The talk about advance fares on that route is academic as they are suspended due to the line closure, That is a straightforward £24.30 Off Peak Day Return (same price if you pay now or on the day), for outward travel after 0910, or £37.40 Super Off Peak Return before 0910.
To Stratford there never are Advance Fares from Oxford so again the question is academic. The fare is £23.20 Off Peak Return on any train- whether bought today or on the day.

Past experience suggests that during an RMT strike such as on 13 May the Bath to London service runs at 50%, ie once an hour rather than twice, at least through typical working hours. You won't go through any "picket lines".

The alternative to the train between Bath and London is a National Express coach. These are comfortable, long distance coaches and not local buses.

The Bath bus station is next to the Bath Rail station.

Oxford to London is a medium advance route - so prices do increase as time approaches, but less dramatically than many of the longer routes.

One to look out for is the less regular train to Marylebone - it starts at £5

And please ignore the reference to "Discount tickets" - that is not a valid term. The person is describing "Advance" tickets.

Just ignore jgdh- While the bridge is closed there are NO advance train fares between Oxford and London either via Didcot or the alternative route to Marylebone.
Even when they are available the Paddington route is now usually cheaper than the Marylebone route- quite a recent change.
So the Oxford Tube is about 1/3 the fare of the train. If they run (and we don't know they will) the trains that do run are likely to be very busy.

This is a very recent video of what the Oxford Tube coach journey is like- https://www.youtube.com/watch?v=_0wV_M1CSrM

please play nice.

ignoring unnecessary. Politeness please