Fault code E133 & E168 Flippin boiler!!?

Hi all I have the potterton pro max boiler too which decided to break down on me displaying fault code e133. I had engineers out who got the boiler going again by replacing some pump. A few weeks later and I wake up to a freezing cold house again run downstairs to make sure the (digital) thermostat was turned up which it was so I ran into the kitchen screaming noooo nooo nooo and began running the tap which had a little hot water left in it but then started to run cold. I ran back upstairs to the boiler (praying that it hadn't broken again) to find fault code e168 flashing. It wouldn't let me reset it but it flared up when I switched it over to water only. Gleefully I presumed all was well and changed it back to heating and water. It worked for a while but then I noticed I was cold and went back to inspect. Fault code e168 was flashing again. It wouldn't let me reset it, I also tried running the tap again and changing it to water only but then fault code e133 came up and that is how it is now :0( I have an engineer coming out saturday but because it is on home emergency cover they only have to get it going again. I would be greatful for any advice of the best thing to do. By the way boiler is only 2 years old. Thanks in advance.