It sounds very much that it is Royal Mail at fault here but surely it is for MB to deal with them not you?
They purchased the delivery service from RM and therefore the contract is between RM and MB. MB have always been top guys when I have dealt with them so I’d be amazed if they did not sort it out for you.
RM parcel delivery in my area does seem to have got worse over last 2-3 months. They always used to just stick a card through the door if there was no one to take delivery which was fine as I would just pick up from PO. I recently found a parcel in my back garden shed (which I rarely go into during the winter) several weeks after complaining to the sender that I have not received it – no card or note to tell me it was there. They have also taken to putting parcels inside my refuse bin, again with no card through door so realistic chance I could have put it out for rubbish collection. Last week I found a parcel just dumped on top of a bag of clothes we had put out for a charity collection by my front door.
Rob