Our puppy was on asda tins when we fetched him too- were phasing him onto burns puppy food, our border collie is on burns and has no problems, no bad stomachs, and its complete so you dont have to worry about them missing anything.
Ours is on 3 meals a day and were in the middle of toilet training too- its a pain in the ass but if you can just watch him constantly for the next couple of weeks it willllll pay off.
we let him out after food. drink, playing or sleeping, and watch him all the time and grab him when he goes in the house. ignore him while u are outside until he goes, and when he does, give him a treat and lots of praise.
hes slowly getting there (or he was, until my OH decided to have him playing in the garden, hes took a giant step back from the angel he was yesterday now- GRRRRRRR!!!!)

ill race you to a clean carpet....lol!

__________________
1.0.0 border collie *ferris*
1.0.0 white german shepherd pup *austin*
0.1.0 dwarf lop bunny *jessica*
2.4.0 leopard geckos *randy, joy, catalina, duckie, petrie & randall*
0.0.2 crested geckos *cherry & dakota*
1.1.0 tokay geckos *mickey & malorie*
1.1.0 chinese water dragons* rhubarb & custard*
1.0.0 anery cornsnake *angus*
1.0.0 royal python *logan*
2.0.0 siamese fighting fish *wayne & garth*

haha good luck with it!!
I think we're slowly getting there (touch wood!), today Cooper has been using his pads but this might be because i layed about 4 out all next to each other in the hope he might end up using them!
Everytime he goes on them i've been really praising him and earlier he went over to the pads himself.
If he does seem to be getting the hang of it i think i'll put one less pad and so on till its just one pad left and maybe he'll go to just that one. I hope anyway!