Thanks h15t0r1an for the tips! I've used the various airport shuttle buses to/from Malpensa a fair number of times in the past, so I'm quite familiar with them. I did not think of using the Malpensa Express from Cadorna though - I've only ever used it from Centrale since they introduced that variant of the service.
It's just me traveling, so taxi isn't really an option unless the inbound flight is well behind schedule.
I think that my plan will be (depending on time and schedules) as below :
a) Option 1 - If I can make the 1900 Starfly bus, take Starfly to Centrale and try for 1925 Malpensa Express from Centrale. Will get me to Malpensa at 2017. Otherwise the 1940 Malpensa Shuttle from Centrale which arrives 2030.
b) Option 2 - If I miss the 1900 Starfly bus, take the 73 to San Babila, transfer to Metro, head to Cadorna and catch the 1958 Malpensa Express from there. Will get me to Malpensa at 2034.
c) Option 3 - Taxi from Linate to Cadorna and 2028 Malpensa Express from Cadorna. Will get me to Malpensa at 2104.
Option 3 appears to be the fall-back in case of delays, weather or any other wild cards.