Have I left investing until too late?

There are retirement calculators online that you can use to estimate your income in retirement. Here’s one that the Australian government provides.

Just about the only thing that can be confidently said about when to start retirement planning is that if you haven’t started planning for it, then ‘now’ is the earliest you have available. Tomorrow will be later, and next year will be later still.

There aren’t any quick answers to your question of whether you have left it too late. It depends on many factors. For example, how much you’ve already saved, how much you earn, how much you spend, whether you plan a quiet or extravagant retirement lifestyle, what your medical expenses will be, etc. Then there are broader factors such as the level of interest rates and inflation, stock market booms and crashes, and so on. You might want to spend time with a financial professional to think these through.

No, it's certainly not too late. The best plan is pretty much the same now as it would have been before, except that you have less time for your money to grow. I don't know about UK specifics, but just save as much as you can (30%+ of your income would be a good starting point), and invest it in a well diversified passive stock and bond portfolio. Don't bother with stock-picking, active management or fancy investment vehicles. Then you'll be able to retire comfortably in 10-ish years.

If you have a big pile of cash now, don't wait. Just dump it all into that well diversified portfolio and be done with it.

IMPORTANT: Consider your stock/bond mix carefully according to your tolerance for risk and time left to retirement. Given the fact that you haven't invested much before, your tolerance for risk is probably low. That, together with the fact that you want to retire in only 15 years suggests that you should have quite a lot of bonds. Maybe 50% or so.

The problem you will have with ISAs is the limit on how much you can invest per year. It's currently £20,000 per year. So even if you have a big lump sum now, you can't invest it all in an ISA.

You may need to invest the rest in a non-ISA account, perhaps feeding it into an ISA at the maximum rate allowed.

If you currently have money in cash ISAs, then you can transfer unlimited amounts to an investment ISA, and that doesn't count towards the limit. Just make sure you transfer the money; don't cash in the old ISA and then try to re-invest the money.

15 Years is surely not too late but it puts you into a pretty disadvantage.

1. You cannot let time work for you through compounding
2. You cannot let time work four you to work out bad times

These two constraints mandate an investment portfolio that is tilted towards safer assets and high contributions compare to a portfolio of your younger self that targets the same investment goals. However, portfolio allocation is one of the later steps in investment. The earlier steps are much more important and they can be performed at any age (and probably should be reviewed on a regular basis even by younger investors).

Quantify your investment goals
You are talking about retirement in 15 years but what does this exactly mean? How much money would you get from state pension, company plans, etc. and how much money will you need? How do you picture retirement? Do you plan to spend most of your day in front of a TV (like my grandfather) or do you plan to be active and travel the world? There is a huge difference between those two variants

Evaluate your financial situation
Make a list of all your income, your fixed spending, your assets and liabilities. How much money do you have left every month? How expensive is your mortgage and if it is expensive are there any prepayments possible? Are any repairs coming up on your house? What about your car?
What is your plan with the house? Do you want to live in it during retirement in which case its value would mainly be not paying rent (as realizing any price appreciation would require selling the house) or do you intend to move somewhere else and sell it (which would actually make it an investment)?

Piece the two sides together Only once you know what you want and what you have to invest, you can properly decide how to invest. Go into yourself and try to determine how much risk you can take. Double-check this with your financial situation. Inform yourself about the investments available and do not trust any so called "advisors" working on commission.