From Probikekit.com:
"The UK postal strikes in July & August are continuing to cause some delay to orders placed in that time period and shortly after. According to Royal Mail there is a current backlog of approximately 80,000 parcels but they hope to clear it soon.
If your order appears to be late then please allow a little extra time before contacting us to report a missing delivery.
We are sorry if you have been affected by the industrial action but at this point all we can do is hope the backlog will be quickly dealt with by Royal Mail."