Hi Stephen,
It may be just a coincidence, that interference started, when you had the meter changed,
according to this PDF below, SMETS2 (which seems to be a system, not a specific make/model of meter)
SMETS2 can use, it's Cellular (Mobile phone) for link up, so any RF output from meter, would be in the 800-900Mhz range
To hear Cellphone Interference, hold your own mobile phone, right near to an audio mixing desk, and make a call

https://www.edfenergy.com/sites/default/files/ifaq-migrated-files/smets2_credit_installer_guide_v.1.3.pdf
Interesting use of words in the section, that says to Installer......
"Objection handling...Customer objections can be common when trying to install a smartmeter.
This is because of the stories they may have heard from the news or from other suppliers.
It’s important to try and manage the customer’s objections before aborting any installs"

I suppose by "stories" they might mean, that in the USA, Thousands of Outside Smart meters were Removed, after some caught fire
and when a householder contacted electric supplier, to say power had gone off, the employees of electric firm, had been told
to hide the burnt meter quickly, so householder did not see it, and possibly take legal action against them

Over here, I read a comment from a UK electric supplier, that said, something like...
"They were happy, that there had only been about a dozen fires of smart meters" ... What! there should be none
Is it the Disconnect contact melting the plastic?, that is causing the fires? Old meters used Bakelite a hard material

It may be Stephen, that your interference is coming from other houses, such as Overhead telephone Landlines with Internet ADSL
that create huge medium wave RFI problems, as do Garden floodlights, and anything with a Switch mode power supply
such as LED lights inside the house, worth switching off each one you have, to see if RFI stops
You mention Solar panels, hold your battery radio near the wiring to these, as obviously you cant turn them off !
the "Inverters" use switch mode methods, to convert the DC from the panels into 240 AC



Rod Watts