Given what we know about
this disease
now, yes, the UK and everybody should have locked down in January..but before we go into full Monday AM quarterback mode yet again maybe it's worth a reminder of the timeline.
www.theguardian.com/world/ng-interactive/2020/apr/09/how-coronavirus-spread-across-the-globe-visualised
I was working "in" logistics/travel
at the start of the year and the feeling end of January was that what we were starting to hear about was was roughly equivalent and would probably have the same effect as the SARS outbreak we had seen in 2002/2003..i.e. clobber air travel in the Far East but no major major effect in Europe....So no, IMHO I don't think given what anybody knew at the end of Jan would have justified shutting the UKs Border's.
Even in early February It was possible to enter/leave very SARS/virus "aware" countries such as Singapore with minimal checks, though there were some restrictions in country..so even the locals in the Far East didn't perceive the full threat...I do therefore think it's unrealistic to expect a UK PM to have ordered closure of the borders of a country sat 6000 miles further west at that time.
Now.... fast forward to end Feb, or early March : That's when the opportunity got missed. It was obvious that the situation was unravelling quickly in Europe and it was then that the penny should have dropped in Westminster...but as we know it didn't, instead we had the infamous football match at Liverpool and of course Cheltenham....
As to the idea closing UK borders completely to everything but freight - no people..at all - just dump "stuff" and turn vehicles and vessels around at the border
......
A lot of the individuals who have worked as crew on ships, aircraft, (plus HGV drivers etc) have been hard at work over the last few months bringing in to the UK not just food, but massive amounts of PPE, meds, and heavens knows what else. Many are Brits/British residents who, believe it or not, would quite like to go home (possibly into isolation) after their often multi-day block of work is finished, and not be consigned to travelling the world forever more.