usually should get next morning unless its in some remote part of the uk its going too. HOWEVER only royal mail special delivery would have guaranteed it for you to be there next morning but does cost a lot more than standard recorded. recorded is only requesting a signature at over end thats it.
for some packet sizes, there's not much difference in price, unless you want the early morning version
another thing in favour of Special Delivery is it has better compensation terms if the item gets damaged or lost in transit