When Can I Renew Without Penalty?

[#1]

We are approaching the end of our 24-month contract for 74Mbs 26 April (41 days time) and when I login to our account it actually says "Your Contract's Ending Soon, Start Saving Cash Today See Your Deals".  When I click on that link I get offered buttons to renew or various upgrade offers, all attractive; the renewal price is actually much less than we pay now.

If I click on, say, the renewal link when does that new contract start and if immediately will I be charged twice for the last month of the old contract? 
Alternatively, if I wait until the next bill being raised on 23 March for period up to 22 April for payment on April 1st, will those great renewal/upgrade deals disappear for worse ones?

Thanks

[#2]

@DavidT As I am no longer a PN customer, and their accounting system seems to have a mind of its own, please take this as 'unverified' advice.

In an ideal world, your new contract should start the day after your current one finishes, but I have seen occasions where the new contract starts the day PN process your request.

As to charges, no, you will not be charged twice for your contract(s), but depending on when your new one starts, you could possibly end up with odd-looking invoices for a couple of months while the system sorts itself out.

Alternatively, you could ring the Customer Options Team on 0800 013 2632 and see if the offer you something even better than the online price, and advise you when the new contract would start. 

[#3]

@DavidT I renewed my contract several weeks before it expired at a better price. I actually phoned in and got a better offer than was showing online.

The new contract became effective IIRC the next day and runs for 24 months, effectively ending the previous contract early without penalty. There were no "glitches" in the accounting, the monthly price just adjusted correctly over the switch.

So, my advice is PHONE them ASAP and see what deal you can get. 😎

[#4]

An update:  I've partially answered my own question in that all my renewal deals showing online have increased in price since yesterday!
Am about to ring them.

[#5]

One thing I've learned about offers, when you see a good one that you're not about to accept, keep evidence in case it goes.