This is more like 3g speeds yet I have cleared my phone of temporary files restarted done a manual roam as well as automatic. Giffgaff says it listens to customers well sort your speeds out or you will lose another fed up with it now
From what I have read on one of Giffgaff updates last year they said in 2017 supposed to be improving bandwidth and data speeds and improving signal but he is the issue will be at end of 2017.