Sorry to hear your experiencing issues using 3G in Swindon.
I've had a check using your works postcode and cant see any issues signal wise from the masts in your area. The works postcode has a mast quite close which is rated excellent for 3G service.
We also don't currently have any faults listed for your area either.
You mentioned others are experiencing this issues also. I would probably recommend calling our Mobile Tech team on 789 or alternatively 0345 6000 789 as they will be able to flag any trends in the Swindon area.