Going home what should I do first ?

I don't think you will have any problems at all since you are still young. I would make sure to open at least a couple of bank acocunts (I also live in SE Asia) and have been with Lloyds for the past 40+ years, but earlier this year opened accounts with HSBC and Bank of Scotland.

One thing I would do is make sure that you are up to date of your NI contributions, and if not, then top up as much as you can. Since I've lived or worked overseas most of my adult life my NI contributions had only reached 6 years (not enough to get a pension) but during this year I've topped up to make it 23 years which together with my private pensions is important. Dealing with the Pensions office is 1,000 times easier when in the UK than trying to communicate with the International Pensions Office.

Yes, get a driving license, good doctor, dentist, car or get used to public transportation which can be really cheap if taking buses.

Since I was back in the UK for about 6 weeks earlier this year, I got a prepaid Vodaphone sim card for £10, but obviously you'd want a post paid one.

Great thing about living in the UK is that car prices, especially 2nd hand cars is very reasonable compared to in SE Asia. I've bought new cars in both Malaysia and Indonesia (I had a big motorbike when I lived in Singapore), but in the UK you can get almost anything you want for a great price.