The rates vary by region and by specific type of contract, so you’d really need an archive document to find the information you’re looking for. If it helps, these were my E7 rates in February 2021:
 

(p/kWh ex VAT, 2-year fixed contract, East Midlands region 11)

There is still an extant tariff table from March 2022, which might help you to extrapolate:
domestic_website_all_tariffs.pdf (ovobyus.com)

It might be easier to help you if you explained what it is you’re trying to work out.  

Thanks, Firedog. I’m trying to establish how much I should have paid for my electricity following the installation of an Economy 7 Smart meter in May 2022 which was not commissioned for 8 months and showed zero on the night rate register throughout that time. I was on a 24-month E7 fixed-rate plan, beginning in February 2021. I was charged all my electricity at the E7 peak rate and want to find out if the standard (i.e. non-E7) fixed-rate available in Feb 21 was less than the E7 fixed-rate peak charge. I was paying 18.57p per kWh peak charge and 11.33p per kWh off-peak (those were the days!). The March 22 chart you suggest doesn’t indicate whether the rates shown there were the same as those available in Feb 21. I guess they weren’t, as a lot happened to prices in the intervening 13 months.  PS. I’m in the Eastern Region.

OK, I get it. 

1. The rates on a 2-year fixed plan should not have been affected by a meter change (or anything else, for that matter - that’s what fixed means!). So your rates will have been given by letter or email when this plan started, and should also be shown on all your bills from when the plan started.
2. The standard non-E7 rate will always be somewhere between the E7 peak and off-peak rates. The rule of thumb has been that the cost of an amount of electricity will be less using E7 rates if the off-peak consumption is more than about 40% of the total, but this varies a lot.  The Energy Price Cap assumes a ratio of 42%. 
3. “… a lot happened to prices in the intervening 13 months.” Sure did. Rates started rising at an alarming rate in 2021; by March 2022 (when the tables were published), the wholesale price of electricity was already four times what it had been when your contract started. 

If you haven’t already done so, I’d suggest you make a note of your meter readings over the disputed period in as much detail as you can. If the meter has been lumping all consumption into one register, you’ll have some serious number-crunching ahead to establish how it’s split between peak and off-peak periods. It will be a tedious exercise, but possibly well worth it. I’ll be happy to lend a hand to help you find the data you need.