Thanks for the additional information.
That's a huge litter for such a small dog but I probably don't have to tell you this!!!
I, too, would be concerned that she's not eating since she's nursing so many babies; they're going to quickly deplete her nutritional stores if her appetite issues continue for more than just a few days.
But, that's great news that she's still caring for her pups and isn't lethargic.
On the off chance that she might be in the early stages of Eclampsia (LINK)
, I'd purchase Calcium supplement pills which should be available at most pet or grain stores. Given her small size and the number of pups she's nursing, this is a condition which might develop even if it's not present now, so supplementation is a good idea.
If she were still vomiting or feeling nauseous, over the counter Famotidine could be given which would be safe for nursing pups. The dose would be 0.25 mg/lb twice a day. This drug may be difficult to find in the UK, though.
One other option which would be safe for her, Omeprazole, wouldn't be safe for nursing pups, so I wouldn't advise its use.
There are appetite stimulants but they, too, wouldn't be advised for a nursing mom.
Unfortuantely, this is one of the problems when a mom is nursing: there are very few drugs which will be safe for her but which won't be harmful for her babies. It doesn't sounds as if her babies need to be hand fed (not yet anyway), but this may be something that you'll have to do if she continues to have appetite issues and her milk production decreases.
Since it appears she's not still vomiting, I'd try to force feed her. I'd mix canned food with pedialyte in a blender and then use a syringe or small turkey baster to dribble or gently squeeze this mixture into her mouth every several hours.
I'd also take her temperture (normal is between 100 and 102.5), if possible since there are post-partum conditions which might cause a fever and thus cause her decreased appetite.
It's possible that her nausea issues affected her appetite; if her nausea has passed, then her appetite may improve, if this makes sense.
However, if she doesn't start to eat on her own within in the next day or so (or if she's running a fever), then a vet visit may be prudent.
I hope this helps. Deb