Changing Shipping Options when order over £30 ?

[Beeunique]

Hi,

At present we have a choice of shipping rates on our website.
We need to offer three options for orders upto a certain value and only one option after that - is this possible?

i.e. for usa we offer airmail, airmail signed for and airsure (with extra insurance), however airmail and airmail signed for only cover upto £36 maximum insurance so for orders over £36 we send ALL orders as Airsure with extra insurance only. At present customers see three options with different prices at checkout for orders UNDER £36 and when spending over £36 the system still makes us show three options so all three show the Airsure (Insured) price as below:

Airmail: £8.00
Airmail Signed For: £8.00
Airsure (Insured): £8.00

As you can imagine this confuses the customer at times so we need it to show the three options for orders upto £36 in value and only ONE option for any order over that value. (We would then do the same to UK and European shipping rates also).

Thanks for any help, the website is www.beeunique.co.uk if you need it

[Beeunique]

Anyone any ideas?
Thanks