Re: the paint issue.
As GIXXERUK has said Hammerite imo as well is definitely good enough for the calipers. Have used it on various cars with good results & no problems due to heat.
Although the price difference between the two is minimal imo.
For example: Hammerite is roughly £7 odd for 250ml and Savage paint is roughly £14 odd for 250ml so double the price but still not exactly a cost too high to pay.
If I was painting my Zeds calipers though, ...I'd go for the Savage paint tbh as G man recommended it is designed for high heat applications and for the cost difference I wouldn't risk the Hammerite this time. Love my Zed too much to skimp on it plus I've no Hammerite left in the garage.