It's been a few years since I did some sustainability modules as part of my studies, so I'm not completely up to date, particularly in the UK, with incentives and costs, but in general being green doesn't come cheap.
Plenty of space for some solar but the return on investment is really a non starter, particularly after the removal of the feed-in tariff. Batteries not so much a problem, as you effectively use the grid as your battery, feeding in when you have surplus, and taking when you need. But I suspect overall your unit cost overall is probably cheaper if you subscribe to a renewables tariff rather than install the infrastructure yourself.
Things like heat pumps are again probably not worth the bother with the relatively few areas that need to heated all week. There aren't that many offices. Perhaps they could look at these for the training ground. Speaking of which, without doing a study, I don't know but the location of the training ground may make it a decent place for a small scale wind turbine. But again, see my point above about cost of infrastructure.
Offsetting could be an option. Planting trees basically. Fairly quick and easy. Plenty of schemes around for this. There's a lot of land in Lincolnshire. You'd hope there'd be avenues to tie up something locally and wrap it in with some kind of sponsorship
How about the T word? Probably not very popular with the players, but electric cars are the future. A few available for travel between the stadium and EPC?