Big companies face a dilemma more than small companies. With a few people a few changes to working practices and your off, plus some can work from home or a rota. May not be easy but is not too hard to organise.
However, the cost of say changing your 5000 person shiny Canary Wharf HQ to be covid safe is in the millions. Plus capacity will reduce by 30-50% anyway - so working from home for many will continue whatever the Government or the bosses want.
Then if covid recedes you have to undo many of the changes again to get capacity back up.
Why bother? You are paying the rent anyway and demanding reductions from the landlords. Just sit it out another 4 months, see if covid goes away. The Bank/Accountant/Agency etc has survived this long, maybe even thrived. If the virus does disappear then great , everybody back in 2021.
If it does not, then oh dear, time to tell the landlord the end of the world is nigh and we are not paying our rent (the landlords go bust with this plan, so rent is never paid in full, the banks foreclose and have to negotiate fractional rates to get the money back on their debt). We wont be needing large offices for a while in that scenario.
So I can't agree with the Government push on this, it makes so little sense for large companies to push for return to work. It is happening a little anyway. France and Germany where they have pushed this have seen a big increase in infections - maybe the conservative british management has got it right?