I didn't include a link, as i think the £100 John Lewis voucher is only for Affiliate offers, so in spirit of the site, i haven't linked this with my own affiliate, so go through Quidco yourself.
I checked out the health insurance quote and mine would work out at under £30 and in return, I would not only receive £115 cashback from Quidco (making a huge profit on top of free Health Insurance) but i would also receive £100 voucher to spend at John Lewis/Ocado stores or online.
Don't forget, that when you use your John Lewis vouchers through Quidco, you'll also receive cashback on this, which means you'll receive a further upto £9 cashback (dependant on the products you buy).
This means i can actually spend £30 to get health insurance and receive (£115 from PruHealth cashback + £100 John Lewis voucher and upto £9 John Lewis cashback) meaning i'll receive £214 in return for under £30 spendature.
Remember to be quick, as the offer expires at the end of May
Hope this helps. :)