Many thanks for the replies, guys, & please accept my apologies about the delay in replying; the kids here are very demanding & distract me.
In response to the question, I have used a dummy load & the SWR is absolutely fine.
SWR is also fine when the rig is connected directly to the antenna.
I too think it's spurious emissions, but I just can't get to grips with why it only happens when an SWR meter is inline?
I will nip the screws up internally & externally on the rig, just in case that's the problem.