Query about Product changing

[#1]

I’m currently on the old Broadband Premier account, but it looks like I’m going to have to change to another product.
My son has been undergoing treatment for leukemia since October, so has been off school since then.  He got an Xbox 360 in December and discovered gaming on Xbox Live. 
With him at home most days, it wasn’t a problem him gaming because Premier is off-peak from midnight to 4pm.  However now that school is back (and he’s just got a headset) he’s starting to use a lot more bandwidth after 4pm when his mates are also online.  This of course is Premier’s Peak period, so our peak usage is starting to go up.
Premier has a 11Gb limit for Peak, so I figured I’d be better moving to a product with a larger quota.  The downside of course is that for all other PN products, the Peak period is 8am to midnight, so his daytime gaming would also count towards a Peak allowance. 
The Extra has a 60Gb allowance, which to be honest we would probably reach (at least until he gets well enough to go back to school!), but does Extra have the ability to buy more gigs if you go over?
Also, I currently have a static address on Premier.  Can I keep this on Extra?
On the other hand, there’s the Pro. This seems to only have a 20Gb allowance, yet it’s £5 a week more.
Can anyone suggest the pros and cons of each one?
Cheers
Dave

[#2]

An extra 5gb is charged at £5.  You can set a limit for the maximum spend per month, after which your line speed becomes significantly reduced until the next billing month.  At the reduced speed, it is unlikely an Xbox Live game would work.
With regards to IP address, I'm not sure.

[#3]

Quote from: Bruce47

An extra 5gb is charged at £5.  You can set a limit for the maximum spend per month, after which your line speed becomes significantly reduced until the next billing month.  At the reduced speed, it is unlikely an Xbox Live game would work. With regards to IP address, I'm not sure.

Thanks for that.  Additionally I've just found out about Broadband Unlimited.  Does anyone know if that would be usable for Xboxlive?

[#4]

Unlimited is a legacy product, so has been withdrawn.

[#5]

if and when you decide to move, you can keep all your extras, static IP, web space etc, but make sure you put it on your ticket that you want to keep then, you can also put a note on the forum, referencing the ticket number as an extra security (one member on Business just this week did not get his IP carried over, but he has got it back)