Can anybody offer adive please for hand rearing / weaning 18 day old puppies. Mum has toxic milk, so puppies can no longer feed. They are a toy breed, nearly up on feet with eyes open.

We have lactol bottles and royal canin baby food if okay to wean?

Definitely, one of my girls a few years back didn't have a single drop of milk after a c-section so I had to hand rear, by 10-14 days we introduced the puppy porridge and never looked back.

Good luck.

Please can some offer advise on amount of milk to give?

We are using lactol we do have the lactol bottle and a mothering kit but none of them will take it, the only way is using a syringe. I have been told they need 4 ml per feed (6 times aday) others have told me they need  around  78 ml per day spread over six feeds. Puppies range is 14.7oz - 21.oz 

We have also started to offer them royal canin mush 4 -5 times per day/night.

I had to start weaning my LB pups at 2 weeks as their mom was very poorly. I had RC milk and starter food but they would not take the milk alone so I tried them on the mushed up kibble, mixed with the RC milk and goats milk and we have not looked back.  They took to the lapping better than they did the bottle. 

if they are managing to lap the food, can you not let them lap the milk instead, if you continue to weigh them and keep track that they are putting weight on then all will be fine.

Agree at 18 days (unless very immature pups) I wouldn't be bothering with bottles, just thickening the milk with soaked mashed puppy food.