[Help] Any advice on being prepared for dog attacking my pup?

Hello,I know there are a lot of experienced dog owners/handlers on here & I've received some really helpful and much appreciated advice in the past, so...I have a7 month old Cav who typically thinks everyone wants to be his friend and is really playful with both people and other dogs.I'm always extremely careful about where/when he is off the lead. My local walks (UK), nature reserve & fields that I use daily are frequented by responsible (my experience so far) dog owners & I've never ran in to anything worse than a bit of rough puppy play.Over the past week I've met two separate people whose small breeds were attacked while on the lead, by off lead dogs (a Staffie & a mastiff-type cross apparently). Both led to very serious injuries & in the case of the former, was lucky to survive.This lady told me she could not get the attaching dog off hers, no matter what she did. In the end, some workmen heard her and came to help, eventually managing to get the Staffie off her Bichon (the staffer owner was not with the dog).I'm so worried about this happening to my pup, and how I'd react. He's my baby & I think I'd just panic.I've been reading about different ways to stop an attacking dog (lift up back legs; twist collar) but honestly I'm not sure how successfully I'd be able to do this, or how advisable this actually is?I obviously take all precautions possible whilst out with my pup & hope this is never something I encounter, but is there anything I can carry with me/prepare for that'd help in this situation?Thank you :-) via /r/dogs http://ift.tt/2sBH527