On some routes it is possible to upgrade to 1st Class for a supplementary fare at weekends and Bank Holidays. Some also allow these upgrades between Christmas and the New Year holidays but not CrossCountry! Click on the following links for more information
A very cheap way of getting to and from London is by taking advantage of special Megatrain fares on the Exeter to Waterloo line. Somewhat bizarrely you need to log into the Megabus web site . Seats will only be available on a limited number of trains and certainly not at peak times. However if you can make it fit, fares can be very low. A recent trawl of the site indicated fares of £8 outwards, £10 back, and £18 for a return journey to London. These fares are not available from the Avocet line, so there will be an additional cost in getting up to Central or St Davids. The further ahead you book the greater the chance of a really good deal
From time to time special offers will arise.
South West Trains occasionally offer an ‘anywhere in their area’ return for £10 but it doesn’t apply west of Honiton.
Two for one offers for entry to major attractions is another regular; see these sites for current offers:
Trade in Tesco vouchers for discounted rail cards and tickets. See this link.