Thank you Jason for the quick response.
I've done all. But the challenge that I have now is: When I added a product that is 30kg in the basket it shipping charges me £23.98 instead of £15.99 since (up to 30kg should fall under 25.01KG - 50.00KG = £15.99) I think how it get to £23.98 was it added (Delivery charge of £7.99 added to all other UK Mainland orders up to 25kg) plus 25.01KG - 50.00KG = £15.99 together. Please how can i sort this out
Below is my rule for up to:
25kg
If session variable exists: eCartCheckoutForm_shipping_country
AND
"based on session variable value"
if the session variable "eCartCheckoutForm_shipping_country" has a value of "GB"
AND
"based on subtotal for any column"
If the subtotal for column "TotalWeight" is ">" "0"
AND
"based on subtotal for any column"
If the subtotal for column "TotalWeight" is "<=" "25"
Flat rate change of 7.99
For up to 50kg
If session variable exists: eCartCheckoutForm_shipping_country
AND
"based on session variable value"
if the session variable "eCartCheckoutForm_shipping_country" has a value of "GB"
AND
"based on subtotal for any column"
If the subtotal for column "TotalWeight" is ">" "0"
AND
"based on subtotal for any column"
If the subtotal for column "TotalWeight" is "<=" "50"
Flat rate change of 15.99