Plusnet Settings - Broadband Firewall, etc

[#1]

Hi I've just signed on to Plusnet - very smooth migration from the excellent (but expensive) Newnet. Ta +net! 
Can I ask a couple of questions about some of the Member Centre settings. The Plusnet Broadband Firewall, at present is set to 'Low'. I'm connected through a wireless modem/router (2Wire 2700) do I need the +net Firewall on at all?
Also the 'Control Your Broadband' settings - do I need to make any adjustments to either 'Set a BB Price Limit' or 'Change my Useage Allowance' as I do not want to be charged for more than how much I normally pay on Option 2 (£14.99/month).
Muchos Gracias 

[#2]

You should be OK with the firewall set to low so I would just leave it at that (you could turn it off if you wanted and rely on the NAT/firewall functionality of your router).  I have a router with a fairly powerful built in firewall but still leave the PN firewall set to low with no issues.
As for the price limit - just make sure that you've not opted to add extra usage automatically on a PAYG basis - you can do that here - you need to make sure that the box at the bottom of the box (you'll see what I mean) isn't ticked.  (In the middle of the panel it will say if you are currently PAYG or fixed.)
If you're on a fixed option, i.e. the box is unticked, you'll be throttled to 128k when you reach your limit but you'll not be charged more than £14.99. (You'll not need to set a price limit.)

[#3]

Thanks Paul, that was very Speedy Gonzalez! 
The panel on data useage says I'm on 'fixed cost' and the little box is unticked. I'll leave the +net BB firewall set to low as well.