Many thanks for your detailed reply. Having had a an MX with an interchangeable screen, even when they are designed for easy removal I completely agree with your cautions.

Has anyone any experience of the Green clean sensor cleaning kit? Not at this stage in respect of cleaning the actual sensor, but are they any good at vacuming dust particles away, again for the focusing screen area and mirror?

Obviously I am fairly new to this forum so appreciate the freeback. It appears to me though that having being cautious from day one on lens changing etc that if dust has made its way onto the focusing screen after six months, are there any regimes that can be suggested for keeping the mirror/focus area etc as clean as possible? Equipment, methods etc...

I appear to have some specks of dust that are the wrong side of the focusing screen. Any suggestions on removal?

I know this has no effect on photo's just extremely annoying...