After hours, if fact almost a full day, I decided to lay the bike on some tyres and pick the tin out bit by bit. I then made a tool (see attachment) that fits perfectly in the inlet holes. 2 mins later out came the filter - or what was left of it.
Unfortunatly if you don't tighten them they start leaking. I've now fitted a jubilee clip to the filter and attached with wire to the rear engine mount. We'll see if it comes off any easier next time.
