Mortgage preparation

TS1962

Here are some facts:

Returning resident after 31 years away, returned to the UK in November 2019.
No UK credit history
Age  : 58
Fully employed for the same company for 31 years, relocated back to the UK and employment is now with a UK registered company. So think of a global company that has offices in 6 countries, the head office is in country 1, I have moved to country 2 which pays my salary and has the legal employment contract, but I still work for head office in country 1.
I have owned property in the UK before but sold before I relocated. So I'm not a first time buyer.
I started renting in Feb 2020 £1350.pm, registered for voting, have a bank account, UK driving license, cell phone contract, sky tv/internet contract, pay water and electric. Own a car and motorcycle and insured and taxed.
NO dependents

What do I want to do?
I want to purchase a small house/bungalow (£230,000)  with a mortgage over a short period, 5 or 6 years, (unless advised otherwise).
I can put down 40% - 50% deposit. - This is money sitting in the bank doing nothing! (Not good)
So I'd be looking to borrow £100,000 - £130,000 (which is not much more than my rent amount over 6 years).

So what's the questions?
How soon could I even think about applying for a mortgage ?
How much does credit rating matter when the lenders investment is substantially lower risk because of the larger deposit?
How can I improve my chances of getting a mortgage? (Credit rating, put money with certain lenders in fix deposit) 
I don't want to wait 3 years!
Regards
Neil