Hello all.
Basically, Britain heavily supported and even came up with many of the various EU policies that they eventually used as a reason to back out of EU membership. Examples being the single market, regional funds, attempting to get Turkey into the EU, ECJ jurisdiction in certain areas, pushing for integration of ex-communist member states and citizens. It goes on and on. Here's a video that goes into more detail.
So yeah, Brexit wasn't at all an irresponsible, hypocritical, bitchy, whiny and stupid move.