Rip off - read the small print

Since we were moving house, we decided to get Shedstore to erect the shed. We spent hours laying the large 8'X10' base of concrete paving slabs. The installation company was not very flexiible on the dates of installation. Ultimately, we had to select a date that we were not at the property. The installation team, came and started on the shed but then decided that the base was not level enough to continue. They took pictures of it and sent it as 'evidence' when I complained. Ultimately, it took 2 amateurs over a day each for us to erect the shed. This was time that we did not have causing other tasks to be delayed or rescheduled. Funny that a couple of non-professionals could use some shims to level it off when the 'professionals' couldn't do it. I think it was to close to quitting time so they couldn't be bothered. To add insult to injury, they only refunded half of the installation fee ("as specified in our terms and conditions" SCREAM) So, they wasted my time, insulted me with photographs and charged £75 for it! I wouldn't even consider booking an installation.
The shed itself is OK but not great quality.