I have on my current contract a 40% discount

My contract expired a couple of days ago but I haven't upgraded as they keep offering me phones at the website advertised price or in the case of the Samsung s7 higher than a new customer pays!

If I go into a shop will they carry forward the discount?

Nope.

I have a 50% discount, I wouldn't renew next February even if they offered an 80% discount.

There are better deals on better networks...

I know but I am lazy so it's easier if they give me what I want

But they offered me one price on me Monday and by weds it had gone up £2 and that pissed me off enough to want to go elsewhere but they say I have to give 30days notice to cancel the contract!

As soon as you upgrade any old discounts are removed from your account. The store will offer you what they offer online. No point going in.

Try third party retailers like Mobiles.co.uk, MobilePhonesDirect and e2save. Their deals almost always undercut direct deals offered by networks and places like CPW.

Mobiles.co.uk and e2save are owned by Dixons Carphone.

Yeah I was gonna but thought it might be a faff paying more now then having to claim cash back every few months unless the way it works has changed

Most of the deals nowadays aren't cashback redemption deals. Times have changed since Dialaphone.

CPW had some pretty good deals on the S7, far cheaper than direct last time I looked (a few days ago).

Check on phoneslimited.co.uk then see the cheapest deal. Sign up for TopCashback or Quidco and click through them to the website that has the best deal. You can get cash back that you don't have to redeem (it usually comes to your cash back account automatically after up to 6 months then just withdraw to your bank account or gift card).