Attribute prices not showing Tax

when adding adition cost to a product in the adribute controler i have been entering the +price number without Tax as once added the attribute the colum above the control shows the price with Tax.

How ever on my stoe is self its showing the price of attribute without tax and is not adding the tax during checkout. Seems ive been loosing 17.5% on all my orders and just noticed since a large order this weekend which ive made a loss on now.

Please how do i get this correct.

example see here.

http://www.fire2you.co.uk/index.php?main_page=product_info&products_id=41

this item has a powerflu option which is showing at 174.95

in admin atribute controler it looks like so
112 Flue Type Power Flue + 174.9500 + 0 0 (buttons here) £205.57 £0.00

how do i get the store to add 205 not 174??

need some help here, im sure its just something i need to turn on but cant fint the right section.

ive entered all the prices to add to my products in the attribute controler without tax. in the dispay once attribute is added to product in the attribute controller show the price with tax (how i want it) but on the store its self the attribute is showing without tax and when checking out vat not being added.

this is a big problem as i need to sell everything with tax for the tax man.

how do i turn this on??

here is the admin screen

here is the product screen

Please help

please help