If a no confidence motion is successful parliament could then go back to Brussels and ask for an extension in order to hold a GE
I think you're chicken is preceding your egg. Parliament cannot request an extension, that power resides with government: "From a legal perspective, Article 50 can only be extended if the UK government submits an official request to the European Council. ".

So, for a vote of no confidence to lead to an extension, the sitting government (i.e. Boris) would have to have to request the extension before dissolving.