First, try rebooting your phone. If you still have issues then check if there is network maintenance going on by going to https://status.o2.co.uk/
Please check what coverage giffgaff (O2) have HERE
Since I moved to Wakefield from Leeds my signal has been very poor or non existent indoors is there a fix that can be used
It's likely you are simply in an area with a low signal level. I have the same problem......10 feet outside of my front door, perfect, solid signal...inside the house, virtually no signal at all. A fact of life I'm afraid.