If your looking for gaining mass, buy some skimmed milk powder. Some may go against this because it contains alot of calories for the amount of protein but i've used it in the past. (seriously, i'm talking about the stuff you might use if you're out of milk)
Blend 100g (or whatever) in with a banana and milk and that tastes great.
For extra cals, blend porrige oats, peanut butter, eggs. I've used all these in the past.
What did you order from myprotein out of interest?
The good thing about that site is you can make your own custom formula, or use one of their tried and tested, that's what I like about it.