Change Broadband product but keep phone Line Rental Saver

[#1]

I'm currently on Extra broadband with Talk Anytime phone. I also payed line rental in advance (January 2013) to get the Line Rental Saver.
I'm thinking of switching the broadband product to Unlimited as it's £1.50/month cheaper and my current cap is 60GB.
I'm concerned that if I change broadband product I'll lose my current Line Rental Saver during the automated product change (through the Change My Product link) and may even end up having to pay it again. I want to leave the phone side of things untouched and just change the broadband to Unlimited.
Is this possible? How would I go about doing it.?
(I also want to keep some legacy webspace, but presume that would remain unaffected)
Thanks
Jim

[#2]

Your lrs will NOT be affected by moving your BB to unlimited. I know I did mine in Dec.

[#3]

During the product change sequence just click on keep my existing product for everything except the change in broadband

[#4]

Done!
I wasn't expecting it to be that simple.
Thanks for the quick replies.

[#5]

Thanks for that I can see the change is due to go ahead on your next billing date, 10th March.