Hiya,
I think the hv's recommed you only go on to hungry baby if they are draining at least 8/9oz per feed, and are still looking for more after that.
The only bad thing I've heard about SMA Gold is that it makes a lot of babies constipated. If you lo isn't and seems to be okay at that end, then I wouldn't bother changing milks, as they're all the same anyway.
How long has he been doing this for? If it's only been a few days then he might just be having a growth spurt. You could try water or a watered down feed at one of night fees to try and get him to stop waking twice.
Good luck!
M