Hi All,
As I say, many thanks for all the advice!

I researched Malwarebytes and for my use case - it looks OK for free install, and to run periodically.
Bottom line for my use case - Great free install - But wait for M1 fix before buy full app.
(A) FREE install:
1. I installed it
2. Installation process was really clear instructions and step through, to get all the permissions set up for it. (For one step - Read permissions or something - I see why DRIVEDX didn't work for me. Shame, I missed out on the free trial period.)
3. I ran it - my M1 MBA has ZERO malware, after months of use without any kind of "anti virus" etc.
4. I paused everything on the app, so I only run when I want it.
(B) For my use case - Wait for M1 fix before buy full system.
Researching it, on MalwareBytes's own forum:
1. There appears to be a current issue where there is a crash bug with M1 Macs, to do with Time machine.
2. User reports He/She is running the paid for app as a free app to avoid crashes.
3. NB: It is also currently still an Intel app, needing Rosetta 2. No eta for native app
Sources:
1. The issue in-depth:
https://forums.malwarebytes.com/top...with-apple-m1/?do=findComment&comment=1430369
2. The work around:
https://forums.malwarebytes.com/top...with-apple-m1/?do=findComment&comment=1444146
Hope the above helps other!
Kind regards
Martin