The Sun are reporting that the fines will be a minimum of £30 and up to £1000. That isn't enough, and in any case we don't have anywhere near enough police to enforce it. They won't do it initially, but when people continue to ignore it they will have no option to deploy troops onto the street with arrest rights.Could be quite substantial fines if we follow the lead of some European countries.
Speaking to a guy in Spain they're handing out €600 fines for people put and about without a valid reason, and for things like having more than 1 person in a car etc.
Taiwan fined a man $33,000 for "maliciously" breaking his quarantine/self isolation.
The problem is that there are a lot of people who won't take this seriously until it directly affects them.