How to add a global sale price without base price reverting to original price?

[Walrus]

I have two prices: £65, and £75 for products. I want to reduce every product by £20 for a short period. This works great when I setup a catalog price rule. I set it up once and it's applied to all products.

 

However, I also have rules for multiple purchases that reduce the price in percentages (5% for 2-10, 10% for 11-20, etc). That also works as expected. 

 

In order to apply the correct discount reduction to the reduced price of £45 in the shopping cart, I have to deselect 'Leave base price' and enter the same price as the reduced price (£45) in CATALOG PRICE RULES. This works but took some working out.

 

The problem is, I can only enter one price in CATALOG PRICE RULES. So, if customer orders the £75 product, reduced to £55, and then selects more than one quantity, the discount is applied (expected) but the reduced price of £55 is also reduced further to £45 as specified in CATALOG PRICE RULES, removing another £10 off the reduced price! 

 

 

Anyone know how to force Prestashop to keep the base price as is for all products, apply the set reduction (i.e. £20) to all products, and then apply any discounts as per setup?

 

Am using 1.6.0.14.

 

Thanks.