I'm in the same boat @Dramalamaindeed... Middle of May wedding.
I've done a lot of reading of the scientific documents and advise, and also the government plans and suggestions - it's not impossible, but it's unlikely that the British government will do anything as extreme as Italy. They seem to disagree strongly with the moves to enforce lockdowns; stating that there is no scientific evidence that it slows the spread.
If there is a lockdown enforced, it's likely to be set to 100 people for indoor gatherings, and 500 people for outdoors. We're just under that, thankfully, so we'd probably be okay anyway... We looked into moving the wedding but if the virus behaves as predicted, we'd have to move it back over 18 months and our venue wouldn't allow it. We didn't really want to, either! Fiancé's parents are probably arguably at risk as both have had recent surgeries, and they called us last week to ask if we would cancel. I'd imagine a fair amount of his family are at risk of dropping out.
We're also hoping that the warmer weather next week brings the expected reprieve...
I obviously can't see into the future and I'm stressing too, not least because I've done much the same as you... years of overtime and stressing and planning and working out and eating well, and it'd just started to feel like it was coming together, the day itself was getting close and I was getting pretty excited about our honeymoon, too! We're due to pass through the US, so that could be pretty touch and go.
But the evidence so far suggests that it'll be okay, and for the sake of my mental health, I'm going to try and keep that in mind and ignore a lot of the scaremongering and uninformed opinions. Generally I believe most people are trying to help, but social media has made spreading panic and misinformation much easier.
No idea if that helps you at all, but I hope it does 