First appeared in February and is now nearly gone.
Get to the GP asap, you can get proper anti inflamatories, mine advised me to use a stick on the other side as that is 3 points of balance and they will also direct you to the podiatrist who will give you insoles or, if you got your own (I got hard, half insoles for about £12 of Amazon) they will stick pads on to tailor to your individual foot. Best to wear in both shoes.
I lived in proper walking boots during the cold months and am now wearing walking sandals (which you can put the insoles in) and Fitflops. I explained to work it was a medical condition and this was the type of shoe I had to wear - it was either this or trainers.
Do the physio regularly; the towel stretches before you get up, pushing against a wall with one foot back and the hanging off the steps. Do the exercises for both feet as sometimes it can spread to the other foot. The podiatrist also advised lying on a settee sideways and opening and closing my legs using the top one
. You are doing foot exercises, calf exercises and this works the muscles a bit further up - equals it all up so to speak.
Yes to rolling the feet on a frozen can of beans and rolling your feet on a tennis ball also helps.
No to walking in flip flops or bare feet (I was told by GP and podiatrist) and yes, for me, that's why swimming didn't help - walking poolside and also pushing off or going down the ladders. Ironing was something that caused me agony - so I either had to sit down or limit it 
You work out when you have overdone it and so have to try to limit what you do to get to a level (if at all possible). I was reduced to bussing everywhere (very expensive) and picking the flatest routes when walking.
According to the podiatrist it was to do with a) age b) gender and c) size of calves. The larger the calf the more you are predisposed to get it.