All bets are off, at least for the forseeable future. Predictions are very difficult in these conditions, as the industry's never suffered such a sudden and catastrophic loss of customer confidence. But I'll have a go! However, I'm as in the dark as everyone else, so any or all of my thought might be rubbish.
There will be a loss of more than 50% of traffic on the North Atlantic and Middle East routes in the short term. That will last as long as there is uncertainty about the US's intentions about going to war. If they actually do go to war, look for traffic to reduce further in those markets.
There is already a jobs fallout from the US and trans-atlantic airlines. Something like 2000 highly-qualified pilots will be released back into the European jobs market, maybe more if the domestic and low-cost sectors start to hurt badly. I'd guess that 2-300 of those pilots will be from the UK, and will be looking for jobs here.
There is unlikely to be any significant airline recruiting for two years; even replacement of retirees is probably out. With a recession now virtually inevitable, there are few prospects for solid airline recovery within 3 to 4 years. In good times, the UK industry hires about 150 pilots a year. In these somewhat unusual circumstances, how long will it take to re-absorb those 2-300 pilots? Many will leave the profession entirely, but I'd guess that these guys (including me) will fill the airlines' needs for the next 18 months or more.
So would I start training now if I were you? No, I'd wait a year or so.
But I could be wrong.