We have Pipex servers in London at Park Royal, and in Manchester having been moved from Nottingham after the closure there.
Network connectivity is not too bad, with only the occasional transient network problems every month or so. The ability to actually provide power, something that is fundamental, is more elusive however.
Since we have had dedicated servers at Park Royal, we have had power issues on 4 or 5 occasions. In the early days when the datacentre was hosteurope, there was no provision for backup power at all, and failures from the grid caused total shutdown of the DC on at least one occasion. Despite the promises that this would never happen again, since having backup power, there have still been failures of the backup system to function as it should.
The latest incident is ongoing. A power failure last night triggered the backup system, however several cabinets are mysteriously not being powered by the backup power, and are down. Our London servers are in one of the cabs.
Luckily we can switch over quickly to backup servers located elsewhere, but this type of problem shows a degree of negligence and incompetence that has no place in the hosting market, and should serve as a warning to anyone considering pipex as a host.
So, to sum up, our opinion of Pipex based on experience is that they are far from offering the "world class hosting" that their telephone system has boasted in the past, they demonstrate at every problem that they are not sufficiently skilled to be able to manage and resolve issues in a timely manner, they do not learn from previous failures, and that until they can get the provision of basic services right, they are not worth considering as a serious hosting provider.