I'm travelling from Brighton to Beverley on 23/12/18, returning 28/12/18. For a change, I'm thinking of going via Tamworth, splitting at Sheffield. There's a £48.20 off peak return from Brighton to Tamworth (Southern and West Midlands only) but National Rail only finds a sole 09:27 departure at this price. All others seem to be £78.80. The only reason I can find is engineering works on the West London line between Clapham and Watford??? Will I be able to buy this ticket on the day and go via Euston?