I don't mean to offend anyone but I am having trouble understanding this thread.
Calpol's active ingredient is paracetamol, which has no effect on sleep. See this study which finds that "Paracetamol did not differ significantly from placebo on any measure of the recorded sleep pattern".
Calpol Night, on the other hand, has antihistamine (allergy medicine that makes you drowsy/sleepy) as well as paracetamol. If that is what you are giving your ds, yes, it will make him sleep. However, antihistamines are NOT physically addictive, especially those put in baby medicines.
So, if you are giving your DS Calpol (just paracetamol) and he is sleeping through, I would guess he is hurting somewhere (teething?) and that is why he keeps waking up in the night.
If it is Calpol Night you are giving your DS, yes, it is probably to thank for DS sleeping through. No harm continuing with it for a few more days until his sleeping pattern is established in the new bed.
Meanwhile, try to (safely!) make his cot smaller with cushions etc. It sounds to me like he misses the cosy feel of his crib and wants to touch all sides.