There are so many wrongs, as I mentioned...totally appreciate the op views, but this was a misinformed and misadvised decision.
Seems, that Eon is aware of the "work" and ok'd it. Mind boggling.
Also, as other have said, unless your ebay meter is modded (which would make it illegal), there are no savings to be made here. All that a electricity meter does is to measure the amount of Kwh being consumed. Nothing more, nothing less. And, if it is modded, suppliers have data points in place to analyse energy consumption, if your consumption suddenly drop without an explanation, revenue collection folks kicks in. There is just so much "energy savings" you can do by change of habits, and they know the patterns.
Energy Suppliers/Meter Operators are responsible for any issues relating to the installation up to the meter. Anything beyond the meter into your property is homeowner's problem. The meter has a unique serial number, and the "cables" that come from the street into the meter also has a unique serial number (Meter Point Administration Number or MPAN).
However, you now have a electricity meter which does not have the installation seal following an authorised installation and as is not owned and installed by your energy supplier/meter operator any problems with that installation now will be at homeowner's expenses.
If an issue happen with the meter and/or meter installation, as soon the DNO or meter operator sees the unapproved installation you'll be liable for their time, call out as you're now the proud owner of your own ebay meter. -- I worked in the industry for over 10 years, I've seen it happen.
I said on previous post, you'll be fine for now, one day this decision will come to haunt you.