I've had one "bad" experience with DPD. Replacement phone, and I was given a late slot (18:50-19:50 I think).
I rang to check that it was going to be delivered, they said yes. I told them I was waiting at work for it, so don't want to be sat here only for the driver to think "ah sod that, nobody will be there" and just not bother trying. I was reassured that wouldn't happen, the driver is on til 9pm, he'll attempt delivery..
The very thing I suspected, happened. I sit next to a window, was staring out the window. No van came anywhere near the building and there's only one access way. Refreshed that page "we could not deliver". Rang and they gave excuses that were all invalid - gated, couldn't access, nobody there, blah blah.
Apparently it was an agency driver, and never actually got a reason as to why they didn't deliver.
They upgraded it to a pre-10am delivery for the next day, and that turned up no problems.
So, with all these extra deliveries they have to make, and extra temp-staff they take on... I'll keep my fingers crossed for anyone that has a late delivery ;-)
On a normal occasion, they've been ace. I've had about 6 deliveries off them in the past and never had an issue other than 2 minutes outside the slot they gave lol but that I can handle.
Wish me luck with my UKMail delivery..