Out of interest how do these shareholder deals work? Is there a minimum amount of shares that need to be owned, or could you say buy one share and be eligible?
My research says you only need one share to be eligible for bt offers. But nominee accounts (what nearly everyone has) do not count. So you would either buy a paper share certificate (expensive), or an electronic share certificate/crest (fairly expensive) or most likely you would buy some shares using the shareview.co.uk equiniti share dealing service who run the official BT electronic shareholder scheme. This is like having an electronic share certificate but run by BT so you address is private but they know who you are. This would cost about £15 for dealing plus £3.50 for a single share.
So it would cost a minimum of about £20 to become eligible for the scheme from scratch. Its not clear how closely bt checks eligibility but that's what the guides I have read say.
For the adsl offer its now actually more expensive to take the shareholder offer than just taking their regular offer available to everyone.
For the fibre if you are on a bt only telephone exchange its an ok deal but still a pricey option. If you are on an unbundled exchange its not really an exceptional deal and there are many other providers who come to a similar price.
Of course you could buy lots of shares and hope they go up and pay for the broadband! Bt does seem to have the market increasingly sewn up these days but whether there is any money in it is an interesting question...