I had a few (not all) of my items switched to Simple Delivery today. These are low-cost items (£1 - £5), where I charged p&p of £1.25. I was able to switch back using the Advanced Options button. However, when I specified £1.25 as the p&p, it came out as £1.50; if I specified £1.00, it came out as £1.20. It looks as if they are going to charge VAT on your p&p charge.

Another thing. They claim the buyer can save £2.28 by collecting  in person, just as if the p&p is still £2.74.