is it more economic to use a zippo than the 25 pence disposables

A Zippo lasts for a long time, in fact it has a lifetime guarantee. The price of the Zippo is basically zero when you divide it by the number of uses. The only costs associated with its use are flints and lighter fluid. The prices of these are smaller than the cost of replacing disposable lighters from time to time, so the Zippo is more economical. I use a Zippo for this reason.

Depends on how often do you lose your lighters.
If you know you will have zippo for a long time, and do not mind the hassle of recharging it, you can indeed save money.

The zippo is more for style. You can also buy the disposables in bulk at costco and sam is club for even cheaper. With that said, I do not condone smoking :)