FloGas accidentally put me on a smart meter plan (and activated my smart meter)..

They can't force you to stay on a plan that you didn't agree to.

Tell them you are cancelling the contract because of a breach on their side. Look to go through their formal complaint process. Move your account to a different provider.

Looking at their rates there's very little difference except at the 5pm - 7pm time slot

27.77c / unit Versus 27.42c a unit 8am to 11pm

32.85 / unit 5pm - 7pm

and then a reduced rate of 21.65c from 11pm to 8am.

my guess is the overall cost difference will be rather small (or cheaper) unless you are a heavy user between 5pm & 7pm and use very little from 11pm to 8am.

That's ridiculous.

You can't request a new meter and a new mprn just because of a simple plan error.

Any difference would be very easy to work out and I suspect that the OP has done better on this plan unless they are heavy users between 5pm & 7pm. The OP could actually work it out themselves in a few minutes.

But lets not make this out to be an error of a huge magnitude - it will be about €50 or so better or worse off.

Raise an official complaint with flogas. Detail your reasons and what you want from them. If not resolved to your satisfaction, raise a complaint with CRU and give your reasons and expectations. Once raised with CRU, it will get resolved

I agree it's ridiculous to have to go to such lengths. My post just outlines the extent the customer may wish to go to be put back to where they should be.

It should never be with the customer to live with an irreversible mistake by a supplier. That too is ridiculous.

What was the outcome of this issue?

Look at your usage and then look at the smart meter rates. Most suppliers made changes in the last year and now a smart rate is far better value that any of the 24 hour rates.

On the smart rates the main discounted unit cost is 24-26c, the "peak" 5pm to 7pm rate is literally just 1.2c - 1.7c higher (it used to be about 12c higher) and then the 11pm to 8am rate is about 13c. The non smart 24 hour rate is about 23c-25c, less than a cent lower than the general smart rate, but no benefit of a night rate

A few small changes and most households could move 30% of their use to the 11pm-8am off peak rate (I've got to over 40%). And that will see a drop of about 20% in your bill.