@noblehead there's a spray I got from Boots (the guy at the pharmacy spent a good 10 minutes looking for it, and found it wasn't properly labelled or indeed priced, and charged me £12 for it!) which I got right when I started pumping - I can't remember the name of it (this is very, very unhelpful I know) but it was designed apparently exactly for the purpose of unsticking stuff like that - well, that's what he told me when I showed him my cannula. It was okay, but brute force was just as effective once I'd got used to it (bearing in mind that I only use ickle flexible cannulas rather than pods - I would think twice about brute force with those, that's for sure!).
When I was a kid (for getting off plasters) my mum used to swear by 'Zoff' which smelt like nail varnish remover.
If it were me having to remove that pod right now given the tools I've got to hand, I would oil up the tip of a cotton bud with something like the sun oil I described above and wipe it along the edges to unstick it. It'd take a few passes, but I'm sure it'd work eventually.