@Levie
I hear ya. I am sick of this intrusive shite. I made one up on the spot some months back ... Said it was sabrefave9999999 @yahoo.com (made up obvs.) They said 'this is coming up as a non-existent email, have you given us an extra 9 or something? Is it dot co.uk???' So annoying that they were able to figure it out (that it was a fake email address) LOL! So I made one up (a mail.com one) as a throwaway one, and just give that one.
I also get sick of going into shops and them trying to upsell.
Savers: 'would you like one of the fragrances we have on offer? Beyonce's is only £30 today.' (That's not cheap for a fragrance I don't want!) Either that or they try to offload batteries onto me!
Then in the Cancer Research Charity Shop they ask me if I would like a raffle ticket - £2. For a raffle I will definitely not win. 
WH Smiths (on the rare occasion I pop in there,) always tries to offload nearly out of date chocolate, and Terrys Chocolate Oranges!
And one checkout operator in Tesco (where I went the other week but hardly use) said I was 'a very silly woman' for not having their club card.
Well, Mrs checkout operator, this 'very silly woman' won't be coming back here again. So you are a customer down now!
That's just a few examples. Upselling boils by blood! Yeah I KNOW they are told to say it la la la. I can still be pissed off by it!
I remember also several department stores (BHS, Debenhams, and M &S, and also New Look and H & M and several other clothes shops,) trying to push a storecard on you! They were proper annoyed when I constantly said no. Just fuck off and process my payment FFS! 
If a shop refused to let me use a voucher if I didn't give them my email address I would absolutely shame them on Twitter, and complain to Head Office.
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