Hi. Thanks for that,Telos, but this procedure does not seem to apply to the latest version of F-secure. In my version, there is no 'Application permissions' setting / tab for example . However, under 'Tools' I do have an icon called 'App and File Control'. Clicking this and the 'Excluded' tab allows you to add files or folders to those items not scanned. I have added Malwarebytes to the list and all now seems well.
P.S. I have now found the relevant section in the Help area on F-secure. I attach it for your reference.
All seems to be well now, thanks Maurice and Telos.
By the way; in your opinion, is it necessary or advisable to run F-secure (or similar) alongside Malwarebytes? Or does MB do all that FS does?