Don't how many travel up north, but here's a Virgin offer for this weekend.
https://www.virgintrainseastcoast.com/weekendflash/
Example fares and routes available
London King’s Cross to/from Leeds - £5 each way (£20 First Class)
Edinburgh to/from Newcastle - £5 each way (£20 First Class)
York to/from Edinburgh - £10 each way (£30 First Class)
Newcastle to/from London King's Cross - £10 each way (£30 First Class)
London King's Cross to/from Edinburgh - £15 each way (£40 First Class)
Aberdeen to/from London King's Cross - £20 each way (£45 First Class