Presenters of property programmes will usually know more about property and building than the people appearing on the show.
People appearing on the show will usually ignore any and all advice given by the presenter (or their builder … or their architect).
It will take longer than you think. (This is especially true if your plan is dependent on good weather … in the UK … in November.)
Doing things yourself may save money but will rarely save time.
Living on-site is always a Bad Idea.
Not visiting the site regularly to manage contractors is a Bad Idea.
There will always be a problem with the structure of the building that cannot be seen until work starts. (If it’s a period property or listed building, this will immediately double your costs and amount of time required … at least.)
I will ignore any and all of the above lessons when it comes to working on my own home.