And people saying "if you can afford £2k+ in rent you can afford to buy" - first it's very weird to assume that someone paying £2.5k must be earning more than £100k. Sure, some might, but that's more than three times their annual rent.
Most people I know, the majority of their income goes on rent. I don't know why anyone would assume that renters must be earning pots and pots of money to the point less than a third of their income goes on rent
Picking up on this, unless things have drastically changed since I left London a decade ago, you wouldn't be accepted as a tenant unless you earned 3-4x the rent pcm. Maybe if you had a guarantor, but the guarantor would have to be in a similar situation ie able to demonstrate they could afford all their own living costs and your rent easily or they wouldn't be accepted as a guarantor.
The thing people mentioned about the back of mum and dad...it's true. If your parents rent and are oba low income, the benefits they're claiming drop drastically when their DC turns 18. Which could mean they can't afford the rent on their place, unless they charge their DC proper market rate rent. Either that or the DC moves out and the parents downsize. Anyone who lives in the family home, where the parent is subsidising them by paying the majority of rent and bills or if the parent owns the home so there is no rent only (by comparison to renting) a small mortgage, beyond the age of 18 is getting a massive amount of help just by being able to live in that situation.
Someone mentioned sheltered housing having extortionate service charges. It doesn't. Sheltered housing is what the council/housing association provides. You're thinking of retirement flats which are private ownership/rental and I agree could be problematic. The group blocks for young professionals with cinema room gym etc would also be problematic with service charges. Housing benefit isn't going to pay for the full rent and services on somewhere with all those extras.
OP if you want to have an understanding of your situation in the future. First get a pension forecast. This will tell you what your pension will be in retirement (if things carry on as they are today for you. If your life circumstances drastically changed so might your pension forecast). Next look up the Local Housing Allowance for your area, input the information needed as though you were your future self at retirement age. This will tell you what you'd be entitled to eg most probably a one bedroom property and it'll tell you the LHA rate for that (can't remember if it calculates it based on income and savings at this point or just tells you the maximum rate). Once you have the LHA rate and your pension forecast, go onto Entitled To website and input details for your future self at retirement, to see if you'd be entitled to any other benefits. That will give you a rough picture of what you personally would have as an income if you were of retirement age today. If you don't like the picture it paints, start working in another solution if you can.
FWIW I think people will end up living in shared accommodation in retirement and it could well be dire. I don't suppose many here remember or were affected by the housing benefit changes a decade or so ago. When they decided that anyone under 35 was only to be allowed the shared accommodation rate of housing benefit. Previously it was those under 25. As an example for someone I knew it resulted in the maximum LHA for a single person going from £80/wk to £53/wk leaving them with a shortfall of £140/pcm on their rent which had to come out of their jobseekers allowance of I think around £70/wk. The previous shortfall on their rent (which was above the maximum LHA) when LHA was paid at the one-bedroom rare was £20/pcm.
To put that into context further, house shares in the area were £3-400/pcm at that time for anything decent. Because people who aren't totally broke want things like internet, TV, heating on when it's cold etc. so the rent reflects that. I don't know what £53/wk would have got them, probably a mouldy room in a HMO in a rough part of town with arsehole neighbors.