One answer related to this from my observations in the US:
By the time all this happens, I'll be in my mid-40's. With all the people coming out of university year after year with similar qualifications to what I will have, how likely are employers going to choose me over one of them?
The is a lot of age discrimination in the sector in the US. The UK will likely be the same based on reading. Be prepared for a lot of unexplained rejections, and some off the wall rejections from folks who don't have a filter.
The folks who "don't have a filter" will say some unusual things. One hiring manager at a leading ecommerce company told me I was too old and he worried I could not keep up with his younger team. We then finished the last 1 1/2 hours of the interview discussing the authentication architecture and problems, and how best to fix it. Another fellow interviewing me blurted out I could be the "token old man" during the team interview.
The IT and computer industry draws a lot of a certain type of people. More precisely, they are INTP's and INTJ's on the Myers Briggs Personality Types indicators. They are highly technical but some are social misfits. A lot of them don't pick up social queues well and say the darnedest things.
They are not being mean. Rather, it is like talking to someone with a mild case of Asperger's Syndrome. I learned about rose-budding from one guy who had an IQ into the 130's. Another time he was talking about the bacteriaAge discrimination in a woman's private parts that make it smell like fish. He could not hold a conversation with a woman, but he could break into just about any server...
As an alternative tothe IT (and after a fair amount of reflection after I got older and my mind got slower)... If you have a choice go into nursing or law. The baby boomers are getting old and they need folks with technical abilities to get through school and take care of them.
Law is a more interesting choice. The legal field needs technical folks for patent attorneys. In fact law school usually requires a bachelor of science for admittance. Bachelor of arts need not apply.
The neat thing about a patent attorneystarts in the US is, you don't have to go to law school. You can study and pass the test to get admitted to the Patent Bar. Also see Becoming a patent practitioner on the USPTO website.
And...
I've been using computers and programming them for over 30 years, albeit self-taught with no official qualifications...
Get certifications and degrees, if possible. Start with the easy ones like A+ or Security+, and try to get a Associate of Science or Bachelor of Science in Computer Science or related field. Remember, you will be competing with a lot of recent university graduates and H1-B's fresh out of school and brought in for cheap skilled labor40's.