Taking a less busy route and reducing the number of changes (for example between bus and train) will help you keep your distance from others.
Guidance for people with symptoms of a respiratory infection including COVID-19, or a positive test result for COVID-19.
www.gov.uk
I don't know if this has been covered in the 45 pages so far but doing the above will only be possible if TOCs run their full services. For example on my last trip I made an additional change at Redhill because the trains from Guildford are not runing to Gatwick Airport.
To be fair to the DfT, I could have gone via Clapham Junction to Haywards Heath but that would have cost more money and my journey was faster via Redhill, due to an unofficial connection at Gatwick Airport. I don't know if a faster journey with more changes is more risky than a slower journey with less changes however.
I don't drive. I did take my test and fail twice, years ago but the insentive to carry on with a different instructor just wasn't there, as I used public transport a lot. I also got fairly within a year or two.
As for riding a bicycle, the other way to avoid public transport, I can't do this on two wheels as I don't have the balance.I could get a tricycle and you can even get folding ones.
However I would need cycling proficiency training to be on the road. Which would need to bring me into contact with other people.