I figured out why the rules were not working :)
I was using the value for eCartCheckoutForm_country as UK but it should have been GB.
I have the page working fine now, thanks for all your help.
However, my client has now asked for another option which I will require the customer selecting an option.
Currently, my shipping options are:
Standard UK Shipping - £3.75
Free shipping on orders over £75 inc vat
International Shipping £5.75
My client now would like a guaranteed next day shipping option with a value of £5.75. I am guessing that if the customer clicks a checkbox for next day shipping I will need to add £2 to the standard UK shipping charge. What would be the best way to impliment this and which page would this appear on, the cart page or confirm page?
Many thanks again