From Birmingham to North Wales best go further north and use the Warrington SC just off the M56. Then it will be Chademos (Ecotricity) on the A55.
If heading into mid or west wales, good luck as there are no SC's at all and none planned. The Ecotricity at Shrewsbury services works well (40 kW) but you may have a long wait if there are Leafs waiting, but I use that charger most days and I've been lucky so far. I've not tried Oswestry but I understand that also works oK.