From someone that started out mid 30's here are some things to consider......
You mentioned "airlines" in your opening post. I don't know if your ambition is to join the big boys or be happy at a smaller outfit.
As you are 40 and have roughly 2-3 years of training ahead of you then you will be finished at approximately 43. Assuming you secure a job straight off then you need to carefully consider what options in terms of a career are available for you should your ambition be to sit in the LHS of a commercial aircraft.
The larger airlines would have a time to command in excess of 10 years. Many are running at 15-20 years plus. As I am sure you are aware the likes of BA, Virgin, BMI, Aer Lingus all reportedly have excess pilots. Some will no doubt be let go in the near future. When these companies hire again the furloughed pilots are usually the first recalled. During this time the time to command invariably "maxes" out although its a moot point as they are not hiring in anycase.
So the big boys really aren't that much of an option to you in my opinion unless you wanted to be a career f/o. And to get into the big outfits you need hours on type which can only be gained from getting a start somewhere else unless you were going to go to Oxford on the integrated route and hope to be picked up by someone like BA straight out of school. The chances of this are so remote (for any student) that I wouldn't be putting the house on it.
So that leaves the next tier of operators. The low cost and charters. The largest hirer of low time pilots is a well known low cost carrier that I am guessing RichT is a training captain at. At the moment they are recruiting at a much lower level than they have historically. On top of your initial training costs you will need to write a large cheque for your type rating and be available to work at any of their bases. You will likely be employed on a contract and paid by the block hour. The amount you earn is dependant on the hours you fly and as has been well documented many pilots are seeing a significant drop in annual flying hours and hence income.
As to the charters companies, well most notably CTC has provided a large number of low houred pilots over the years. Their holding pools are full of freshly qualified people that have jumped through numerous hoops to sit waiting for a start. The holding pools are growing by the week as no one is hiring to any significant extent. The "newish" trend to employ pilots on summer only contracts and then release them back to the hold pools is a disturbing trend altogether.
Next on your list are the regional operators including the turbo props eg: Flybe, Southwest, Aer Arran etc. This I think is your best chance. Time to command can be relatively short (say 3-5 years) when the market picks up as "generally" many of the younger pilots will seek a move onto jets creating spaces. Your age can be an advantage with these operators as you may be seen as someone they can rely on to hang around given your maturity and possibly family commitments etc.
Additionally there are the biz jet operators, freight and other niche operators such as air taxi and medivac flights. Many of these jobs go unadvertised and selection is through word of mouth recommendations so networking will be important.
All in all there are so many ifs and buts to consider but at the end of the day the only person holding you back is yourself. If you go into it with eyes wide open and adjust your goals accordingly then you can make a career out of it. But do research in detail the terms and conditions that you are likely to earn as the return on investment can be quite poor.