I would broadly try to keep things business as usual. However:
Shielding to be on a voluntary basis with government support
This would ensure that those people who have very understandable concerns about their own health if they were to catch Covid-19 are supported in avoiding the risk as much as possible.
I would legislate to allow workers who feel that their individual circumstances do not allow them to go to work safely and where their employer could not allow them to work from home to be able to have paid time off work (with appropriate government funding like the furlough scheme) to allow them to stay indoors. Additional funding would be provided to councils to set up support services (eg food parcel deliveries for those without friends or family support) and additional funding provided to local NHS primary care facilities to ensure that such people received the healthcare they needed via home visit. Where jobs have been left vacant by those voluntarily taking funded shielding, provide a facility for businesses to use (a bit like the jobcentre website or whatever it is these days) to advertise temporary vacancies to cover the roles, which may be popular with casual workers.
Encourage those who can work from home to do so
This will take pressure off public transport and the road network.
Working from home means that there is a broadly smaller geographic area in which an infected person could spread the virus and it prevents one infected person from closing down an entire business, or potentially, industry.
Provide a technology fund for small and medium businesses
This will ensure that small and medium businesses are able to play on a level playing field with larger organisations who tend to have more money to spend on tech tools.
Technology is essential in the 21st century, but many small businesses don't have the funds available to meet the changing needs of their customers. I was in an independent butchers in Manchester last week trying to support small businesses, and it turns out they didn't take card - so I had to go and buy my things from Aldi instead. This fund would allow shops like that to receive a grant to purchase things like chip & pin/contactless systems, buy a laptop so they can take enquiries via email, have websites built for them so they can sell their wares online to those who are voluntarily shielding, and potentially for restaurants and cafes to link up with third party delivery services to expand their market.
A structured, joined up, and consistent communications strategy
This will ensure that there is no wiggle room or opportunity for confusion or misinterpretation.
Currently, what Boris says, what the government website says, and what the law itself says are often three different things. This leads to, for instance, the Barnard Castle incident. Any laws will be written first of all, and then, the government website will be updated clearly stating each legal requirement and explaining it in simple terms. Any communication from the PM or government ministers must reflect the law and not include things like "we advise" or "you should" - it will be, "this is the law, and you must follow it".
Requirement to self-isolate if you have coronavirus symptoms
This will ensure that once a potential case has been identified there is reduced risk of it spreading.
Pretty much identical to the current UK Government requirements, those who are exhibiting symptoms consistent with coronavirus to self-isolate, with a legal right to time off work on full pay.
Things which would not feature - Covid-Secure Requirements (whilst social distancing guidance and advice would be provided, a business should be free to choose what measures it puts in place based on customer demand and staff views, the business which does this in the best way will naturally be the most commercially successful), Face Coverings (they cause more trouble than they are worth and businesses can provide alternative methods of separating their staff from customers, eg perspex screens, should they choose to do this, and those who feel they are not safe outside whilst people are not wearing them can get government support to stay inside, as above).