Thanks for your input Paco.
I also noticed the marriage for John Bewes in St Stephens by Launceston, but it states that he was "the younger", in which case he would not have been the brother of my Alice Bice, whose parents were Robert and Marion. I haven't been able to find a baptism for an Alice Bewes in St Stephens, but it would possibly have been too early for the records.
I've been researching the my family tree for quite a number of years now, and I'm still learning (and at times struggling). Part of the problem with the Bice branch is that their surname was often misspelled. I picked these variations up off the Internet yesterday:
"Includes Baer, Bair, Baire, Bairs, Bare, Barr, Bayer(s), Bayes, Bayre(s), Bays(e), Bear, Beus, Bewes, Beyer(s), Biar(s), Bias, Biasa, Bice, Bier(s), Bise, Bower(s), Bowyer, Boyars, Boyer(s), Buias, Buis, Buyer(s), Buyor(s), Buys, Byan, Byar, Byarse, Byas, Bye, Byer(s), Byiers, Byire, Byor, Byre(s), Byris, Byrn, Byus, and other variant spellings."Other variations that I’ve come across whilst researching this branch of my family are: Bysse, Byse, Besse, Boies and Byssett. I've even come across a marriage where my ancestor's name had been transcribed as "Wise", because of the old-fashioned way of writing the capital letter "B".
However, this kind of challenge is one of the aspects that makes genealogy so interesting!
So, to sum up, as Bewes is a known variation of Bice and, given the names of the children of John Colquite and Alice, it's still a possibility that Alice was the daughter of Robert and Marian Bice.
Similarly, the Bewes family from St Stephen by Launceston could be related to my St Enoder Bice family.
Thanks again.