Getting witnesses shouldn't be a problem. They're only witnessing that they've seen your mother, and you, sign the forms. They don't even need to know what the forms are about. (Anyone over 18 can do the job, except that you can't witness your mother's signature). As an analogy, the witnesses to my will were just two people I happened to be working with that day, who provided their signatures in a Tesco car park.
You'll also need a 'certificate provider' who is simply someone who can confirm that your mother freely consents to the LPA and that she understands what she's doing. That could be, for example,a health professional or simply another member of your family.