People will certainly take the piss. Like they have done recently in their 'mass hug' protest bullshit (can't remember where, probably London).
Having said that, they are minority despite being a news story. As much as I think there have been selfish cunts and a lot of people out there showing a sheer lack of common sense, on the whole the public have been fairly tolerant and adhering to the rules.
I really hope that when lockdown is relaxed, even in small measures, people dont' mistake it for ultimate freedom. Whilst it may feel like that, the actions have to be restricted still. I can imagine there'll be copious amounts of people going straight to house-parties and parks and social gatherings. It's why I think police rules need to be tougher - increase the penalties for breaking the rules and you're more likely to stop the behaviour. Dishing out fines that probably won't be paid or chased up hastily isn't going to deter people.
The government message has to be clear though and it's why the exit strategy needs to be transparent. Explain the risks as basically and clearly as possible. Explain why a second wave would be catastrophic (or at least what damage it could do). Explain why going hell for leather at the first moment of relaxation is not the most sensible thing to do.