Please forgive me if you all already know this but I thought I’d share it on the off-chance that it helps somebody else.
I was given a Hotpoint WF340 to repair and re-sell, when I powered it up most of the lights were flashing rapidly, luckily I had a control board from another identical machine so quickly narrowed the problem down by replacing the board.
Looking at the faulty board one of the capacitors (C17) was very obviously domed.
Replaced the capacitor and it now works fine!