Butterscotch Bailey's Muffins

I rustled these up this morning while I am having a new carpet laid in the dining room. They are meant to be for a bank holiday BBQ at my daughters today, but they smell so lovely I imagine they won't all get there. The carpet fitter is looking hopeful that he is going to get to sample one with his mug of tea. And naturally it would be rude to let him eat on his own - maybe I'd better bake another batch for later on.

In a large bowl mix together:
375g self-raising flour
140g soft brown sugar
60g caster sugar 

In a small bowl mix together:
90g melted butter
half cup sour cream
quarter cup Baileys
tablspoon strong coffee diluted in the minimum amount of boiling water (half a quarter cup)
2 large eggs

Mix the wet into the dry then stir in:
100g white chocolate chunks
100g butterscotch pieces

Divide the mixture between 12 muffin cases 
Bake Gas 5/6 for 20-25 minutes
Leave in the tin for a few minutes before removing onto a wire rack to cool