I think it’s just demand, can’t see how a week-long break in the supply chain would take months to correct, plenty of stuff comes in via other routes (timber from Northern Europe, and still some stuff made here). People haven’t been able/willing to get work done during lockdown, also time spent furloughed or working from home gives you time to contemplate your surroundings and scheme what you would do to change it, or identify the need for a home office / garden room for wfh Etc.
Apparently the cost of building projects has increased massively, here in the south-west supposedly by 27%. We can’t even get anyone to quote for our flat refurbishment, people are booking work in for next spring. What we will be able to afford to do is likely to be less than planned which is a bit of a shitter.