Quantity Discounts for 1.3

I have no idea. I have never seen this situation. I would have to analyze your site to figure out what's going on.

Is there a place I can send you login information?

Please see your PM if you want to hire me.

I have just installed this and I think I have an issue as I am also using Reward Points Module.
No discount is showing at all in the checkout pages.
Could this be the case?

They don't interfere with each other. How have you configured Quantity Discounts?

I was aiming at discounting each product by 10p when hitting over £18 total, 20p each for over £36 etc

Include Tax
true

Re-calculate Tax
VAT

Discount Units
currency

Discount Basis
Total By Item

Counting Method
currency

Discount Level 1
18

Discount Amount 1
0.10

Discount Level 2
36

Discount Amount 2
0.20

Discount Level 3
72

Discount Amount 3
0.3

I suspect you want Discount Basis = Total Items in Cart. Right now it is saying if you spend over L18 on a per item basis, you get this discount.

even if I change the value to
Total Items in cart
Counting method - Currency
Discount level 1 - 3
Discount amount - 5

the total still remains the same in the cart.

Just realised this is in the wrong thread.
I have version 1.5.1 so will post there.

It's called "for 1.3" because it was created when 1.2 was still in widespread use. It works fine in 1.5. You have some sort of issue (likely related to another mod or other change) in your cart that is preventing it from working; you're going to have to get someone to look in detail at your site. I can't debug this sort of thing over the forum.