There is travel advice for getting to Wasps on the LISC website
There is a bus from Reading to Wycombe, and a free shuttle bus from Wycombe Railway Station to the stadium (it is a few minutes walk from the bus station to railway station). Last bus back to Reading is at 6:15pm.
It is 1 hour 20 minutes on the bus from Reading to Wycombe + time to get from the town centre to the stadium, so not the quickest route, but at £6.40 return it might be the cheapest.
For drivers, there is a park and ride at Cressex, which is just off the M40 J4 and also a number of car parks near to or at the stadium - it appears the cost of parking increases as you get closer to the stadium.
Can't comment on whether the LI Pubs coach will run or not - I haven't seen or heard from them since the excellent Edinburgh trip - maybe they are still recovering