First, as it currently stands there would be no problem, entering the UK. There are currently no active restrictions for the UK for foreigners. You and your wife could enter the UK if you would need an overnight transfer.
For Spain, the previous poster
mfkne is not making a joke. You could speak with the Spanish Embassy in Japan and discuss your options.
By the way, doesn't your wife have a residency permit in Spain as she is an immediate family member of a Spanish citizen ( you )? If so, that should be fine.