Wednesday night is never going to be lots of fun in a pub/club with only 4 of you to make the atmosphere so you need to do you own thing. Can Wednesday include Wednesday night/evening?
Assuming the others are outdoor orientated a more memorable event would be an "adventure". Set off from point x on bikes, maybe head to the coast via nice country pubs. Trip out on a touristy fishing boat trip (easy to sort in your area, thinking lyme regis type location) and catch your own mackerel supper. Head to beach or campsite(check out cool camping for nice ones in your area) that allows camp fires for a chilled out few beers and evening cooking your catch. Replace sea fishing with trip to fishery if you want to keep it inland and it works better with camping location.
Or…. there is a place not a million miles from you (I think near Devizes) where you can hire canoes and paddle down the river, camping out on the bank along the way. They pick you back up however far down the river you arrange the next day. Again, mellow chat, small fires and chilled beers and all pretty memorable which is what it is all about. I can find out the details of the place if you want them.
I've always felt activities that allowed a bit of a group love in and discussion where you can work together, chat and "bond" whilst doing what you are doing work better than solo activities where you can only talk about it afterwards (thinking gokarts etc).