is there anyway Pre 1900 any stable welsh, scottish and Irish kingdoms/republics can be created out of the UK?
And also what would that do to the British Empire later on? would we see Irish holdings, welsh colonies or scottish east india company?
As others have said, there have been myriad other threads about this. There are hundreds of ways Scotland can remain independent, Ireland can revolt, and a few ways Wales can, though once it's been annexed then it becomes much harder to reason for the creation of a Welsh state because until recently the Welsh weren't fiercely independent in the same way the Scots and Irish were.
To answer your second question, though, it's unlikely. Ireland had a running period of adversity with its own Parliament and the Catholics had no power, locally or nationally, until Catholic Emancipation. Likely Irish independence would be followed by a period of weak government as the country struggled to work out how it should govern itself and who should govern it. Also, the French and Spanish expressed a desire repeatedly OTL to conquer Ireland and would likely do the same in TTL, "for the good of the Catholics". Either way, Ireland was pretty poor and unlikely to manage any colonisation. Scotland had a similarly poor local economy - indeed, this was the very reason for their union with England. The Scots attempted to found a colony in Central America with the Darien Scheme, but it was poorly thought out and they were completely inexperienced in colony-founding. As a result, the colony was a disaster, and barely lasted three months. That one colonial attempt virtually bankrupted the country - it is estimated to have costed 1/5 of all the money in Scotland, and that is an example of Scotland's poor economy, not how much they spent, the Darien Scheme was relatively cheap - and that cost forced them into reliance on English money, which facilitated the Act of Union 1707. Scotland just doesn't have the money to try colonialism, and even if it managed it, it's likely to have its colonies conquered in record-quick time by France, Portugal or the Dutch as it has frankly no way of defending them at all. The Welsh did manage to colonise Patagonia, but they always knew they could never do much and kept their attempts extremely low-key - single colonies with only a few hundred people in a couple of places and that was it. Again, it's unlikely the Welsh could support anything more.