This has been recently discussed in another forum.
The objection to Italy applying more strength to Greece is the usual: logistics. The Albanian infrastructure is abysmal (small ports, no rail, no roads).
The objection to Britain remaining neutral is that Britain had issued a guarantee to Greece a month later than its guarantee to Poland. By the fall of 1940, Britain had already been seen as unable to do much for her allies (Poland, France), and could be construed as clumsily dragging neutrals into the war without being able to help them either. If the Greeks ask for help, the British can't ignore that.
OTOH, it's possible that, also by concert with the British, the Greeks initially try to handle the issue alone exactly for the same reason as in OTL: preventing German involvement. The British will of course send arms, maybe more so than in OTL given that they aren't fighting in the African theatre.
Naturally, the belligerent Italian governor of the Dodecanese will react predictably: Italian submarines will begin hunting British cargo ships, without a DoW between Italy and Britain. They might be less successful than with Soviet ships during the Spanish Civil War, but something they'll get; conversely, the British will convoy with escorts, and they may soon in turn sink an Italian sub, or worse damage it and force it to emerge for the world to see.
Either side (Italy or Britain), or both, will end considering this enough of a casus belli.
It certainly isn't in the British interest to do this, but consider how in OTL Churchill was willing to damage the ongoing operations against Italy in Africa in order not to abandon Greece.