I have an MPAN also, so would be the same process as you.

I just need to decide if it's worth the couple of hundred pounds to get a few pence back for each kWh exported from the battery during the summer.

So while the Octopus process was not a "no win no fee" type of process, it was a calculated risk. Before the summer it will have paid off. Hope that it works for you! 

Thanks for the update.

I'm glad it is possible, I just have to crunch the numbers in how long it'd take to recover the fee at around 8-10p a kWh difference.

How was the process for getting Octopus to agree to export without an MCS certificate in the end? Did you have to pay anything?

We also don't have an MCS certificate and I am interested in exporting in the warmer months when our battery bank will have plenty of spare capacity.

Yes, it was a very reasonable payment. Less than 10% of the £3200 the full MCS service would have costed us (of course not directly comparable)! 

So I submitted the SEG application to Octopus. Fingers crossed, perhaps it will not be tripped by any silly building regs "checking the checkers" process.

This is what worked with a few iterations. 

The regulation mandates labels indicating that there are multiple generation sources in the site.

Would you care to say which regulation you're referring to?

When I was looking for the regs for labelling when introducing an inverter able to export, I started with some of the questions present in the G99 commissioning form like: 

• Generator’s Installation satisfies the requirements of BS7671 (IET Wiring Regulations). 
• Suitable lockable points of isolation have been provided between the PGMs and the rest of the Generator’s Installation. 
• Labels have been installed at all points of isolation in accordance with EREC G99. 

As I wanted to make sure the electrician would have the required labels, I bought a set of labels that was suitable for a PV installation in advance. A subset of these were then applied in and around the consumer unit and inverter. By this I mean something like the set below: 

For guidelines and an overview of labelling, this IET article may help.  Ultimately qualified electricians have access to the current regulations. 

And of course, always make sure to use a registered electrician. 

My learning in this process will be to argue more robustly (and immediately) when an electricians' firm (no matter how large) claims they can replace your consumer unit without notification.

But it's a misinterpretation of the regulations by Solis.
Their inverter can't 'know' what other in-house devices are counting towards the export levels approved by a DNO.

This Solis inverter being rated 8kw and (I expect, as I did not test) also allowing export of max 8kw, it should be operating to g99 when connecting to the grid.

The solis does allow the voltage on the backup port to be independently set. But that is only effective when the grid port does not sense power and the port is fed from dc sources  (perhaps also if the grid power is outside the expected parameters). In normal circumstances, the backup port power mirrors the grid input. 

But it's a misinterpretation of the regulations by Solis.
Their inverter can't 'know' what other in-house devices are counting towards the export levels approved by a DNO.

This is the sort of detail I feed back to manufacturers.
In this case it would perfectly satisfactory to have configuration 'G98' because that's what they were required to test the inverter for.

Provided that setting still allows you to configure export levels above 16A/phase, then there is no reason why there should be an option to define 'G99' in that field.

Based on the fact that the DNO approved 8kW export (so over 32Amp), I understand that I should keep it set to G99.