With a bit of planning monthly train season tickets can work out cheaper than an annual. A monthly doesn't have to be for 30/31 days, you can buy them for any length you like so make sure one expires just before Easter/summer hols/Christmas and then you're not paying for one when you don't need it.
Thanks, I did wonder about that. Likelihood would be first 3-6 months would be in the office, but would try and introduce some working from home after that, so annual would make less sense I guess.