There is a bit of a myth that supply and demand keeps prices at the optimal level.
This is only true if you take a medium term average.
That happens in the short term is that prices go up, or down in steps.
This is because of production capacity. So say you have a factory that can produce 1,000,000 bricks a week, to make 1,000,001, you need a new factory. It makes that extra brick quite expensive. So what happens is that before the major investment is made, prices start to rise, regardless of production or sales volumes.
Perversely, this also happens in the reverse situation, This is to pay the costs of reducing production i.e. righting off capital expenditure, staff redundancy payments, relocation expenses, different marketing strategies.
With small companies, that may have overproduced and then gone bankrupt, there were bargains to be had at auctions. This tends not to be the case with larger manufacturers and suppliers. They now go into pre-pack administration, fail to pay their suppliers/landlords/councils, but don't pass on those savings to the consumer. Or sometimes they get bought out by another company that is in a similar or allied field. Buying up a competitor is a good way of charging more.
Now a quick look at the UK economy on Wikipedia shows that 1.5% is agriculture, 18.8% industry and 79.7% services (2016 figures).
So where would you sensibly put your money, in agriculture or services? Industry is quarter the size of the service sector.
It could be argues that agriculture, being so small, has the greatest potential for growth, and if you listen to Farming Today, they seem to think that the market will be challenging, but have greater opportunities. This may or may not be true, but I suspect that the opportunities are for the land owners, rather than the people doing the actual work (we have some odd tax rules around farming).
Many think that once we are free of EU rules and regulations, and even if we just trade under WTO agreements, we will be free to buy from whoever we want. Ask a USA dairy farmer how much they now sell to Canada, which has an agreement with the EU to buy 80% of all their dairy from the EU, in exchange for concessions to sell grains and metals to the EU (they can sell a few other things as well). Canada was not a dairy nation, but it wants to do more trade with the EU, so the deal they agreed did not affect their economy much, probably reduced prices, but it has locked out trade with some other nations. The knock on affects of this are currently unknown.
So for Canada, they got a good deal, the EU got a good deal, for everyone else, not such a good deal.
So this idea that the UK can freely trade 'with the rest of the world' is nonsense, there will be restrictions, usually financial.
This is why one of the UK's economic successes, the banking, insurance and financial services is moving registered offices and personnel into EU countries. The bulk of our earnings, as a nation, is in those sectors, neither the UK government, or the EU parliament are in the least bit bothered about the cost of bricks or windows.
If you take cement production in the UK as a proxy of general construction, then the figures are not looking good. There was ~2% decline in 2016, by 2018 the market was 4.5% smaller, but the cement industry put a glossy spin on it saying that sales had increased. Increased from a lower base. Capacity has been taken out of the market and prices have risen above general inflation. Much of of the supply has been for large infrastructure projects, mainly Cross Rail and the hope of HS2. Cross Rail is at an end now and HS2 may not happen, nor will the Severn Barrage. Or a new London Airport.
So where does all this leave us.
In a tight place financially.
Expect price rises, harder to source materials, lower quality and less choice.
Refurbishment may be a better option that new build.