So you removed the default external antennas? Those are 4G signal antennas. The main signal strength depends on the sim card and the ISP. I don't think changing any settings on the router would make much difference.

Many thanks thats what I suspected, it seems like the exterior aerial has little use
I think the problem is in the router settings somewhere though, I have 3 bars lit on the display but just get the message " safari cannot open the page because the server cannot be found".
When I first set it up I had no problem, with an excellent download speed (20-30+) I think the settings may have changed somehow.

You cannot login the admin page of the router? Did you try login from another device? Or reboot/reset your router? Do not connect any other modem to the tplink and try login. If it's in, you can connect the modem back to tplink.

I have reset the router and the problem seems to have cleared. Many thanks for your help.