This page tracks Scottish polling for UK Parliament elections. Unlike for the Scottish Parliament, there is no tracking of seat projections, as the purely FPTP nature of the UK Parliament makes those even less reliable than normal.
The 5-poll average is an arbitrary measure that is provided to give some sense of how support is shifting over time. In countries with more regular polling, something like a 30-day average might be used, but given Scotland is lucky to see one poll a month outside of election campaign periods, we have to make do.
Redfield & Wilton Specific Note: Due to specific issues with inconsistent house effects, Ballot Box Scotland no longer reports on Redfield & Wilton polling. Previously, there was a policy of only including one of their polls in the rolling average. This is explained in more detail here, but it is not a circumstance I particularly relish being in.