Ah, I now have the definitive answer from Peter himself regarding the labels:
Generally, the "individual" pieces are signed, and production works had the sticker - as far as I can remember used from '77 or so to '84. I haven't used stickers since then.
So that's an excellent guide and the signed ones are worth looking out for. Peter employed a few glassblowers, so I expect the labelled ones were 'generally' produced by them.
On another matter, Peter has some 6-page A4-sized leaflets (folds together to A4):
The catalogue was produced for a crafts trade show in Dubai that I attended in the late 70's. The Ocean range was the actual production range; the others were individual pieces, but given the Pearl and Coral names for the Dubai show. I've only made a few pieces since returning, using a local glass concern.
Again, some useful information in helping to identify and date his pieces. He has also offered these catalogues to anyone who is interested - there's a whole box of 'em - and he has given me permission to upload the six pages here, but I need more than the 125KB limit of GMB so perhaps in the Glass Galler (© Peter Tysoe)