Hi SleepyCompass
Royal Mail no longer offer a service termed " recorded" but they offer " signed for ". Signed for is best for an item which is of little value but where you want proof of delivery. It is delivered in the same sack as all the regular mail and is not tracked. The only difference is that a signature is required.
I would recommend sending important paperwork relating to PIP or the WCA by Royal Mail Fully Tracked. It does cost more but is separated from the normal mail and its journey is tracked and delivery is verified usually with a photo.
I cannot see how Fully Tracked can delay delivery by more than 48 hours and there is always the Next Day Guaranteed service.
David
Nothing on this board constitutes legal advice - always consult a professional about specific problems 
