Anne, do you have a 'Wilkinson's' near you? or perhaps a 'The Works'? I think they have a school glue, failing that how about WHSmiths?
As Margo says, make sure that it says
washable on the bottle and then it will have to be a case of try it & see. Personally I am chary about using glue in embroideries, since I was warned off it at the RSN, and the warning hasn't completely worn off yet
, but that is not to say that it is not a useful idea, provided you have tested it prior to using it on the 'good piece'.