I think it's money well spent in the context of the price of moving house overall.
People forget that long distance moves cost more too - often 2 days work and accommodation due to limits on hours that can be driven or worked.
Paying a few hundred quid more for the professionals, often means you have a very large van and several workers who are trained in assessing how long a house will take to pack, can do it quickly and efficiently without emotional involvement in the stuff, can load the van in the most efficient way and get everything in. They do all the hefting about of heavy stuff which is absolutely exhausting to do on top of the stress of moving, cleaning the old property. They have all the right gear in the right quantities and you don't find you're 3 boxes short or you've overloaded a box and can't move it. Plus they do it all in the day or two before you move rather than self movers who often find themselves starting to pack weeks in advance and finding themselves living surrounded by boxes and living out of them, as exchange dates don't happen when expected.
On arriving at the new property, when you've got movers, you can rush in, look round and be excited. The movers will shift all the gear into the right rooms, up the stairs and literally do the heavy lifting. If you've already had to do that on the way out, even with a friend or 2 to help, you will be a wreck by the end, unless it's a first move and you don't actually have much stuff. In my mind, for around a grand, it is so worth it and I would always factor it into the list of costs of moving.