In London I find the Royal mail absolutely appalling. Important things like credit card statements regularly don't turn up. First class arrives a week late etc. On the South coast I generally find things a lot better. The postman is superb, kindly going back at the end of his round to get signatures for parcels or letters. I think the problems have come through the cost cutting exercises. The post(wo)men on the whole are very good, but they are limited by the behind the scenes operation.
I find Parcel Farce one of the worst delivery companies (see my post parcel farce!) They have closed some offices and the service now stinks. Instead of Shoreham (which was excellent, now sadly closed) the parcels come from Redhill (service stinks!)