If the car has runflat or tyre pressure sensors then I would not introduce any gunge inside the tyre.

Thanks for those replies. I was nearly put off by the lack of a spare, however I do like the car in general. It is surprising how many cars are now sold without a spare. They do provide a bottle of gunge and a tyre compressor to use when you have had a puncture, no use for serious damage to tread or sidewalls of course, that will mean roadside assistance and tow to a tyre supplier.

The stuff I am considering is called Ultraseal (i think) you put it in the tyre and when a puncture occurs it seals the hole. You would not know that you have had a puncture.

Has anyone any experience of this stuff? I am also considering buying a spare wheel and tyre.

Posted by me on another thread here on technical:-

I have used Ultraseal on both cars and motorbikes for years. The primary reason for me doing this is I don't want to be stopped on a busy road with a puncture-especially on a motorbike. The most dangerous place to be on a motorway or dual carriageway is the hard shoulder.

Never had a problem with the stuff-does everything it says on the bottle as long as you stick rigidly to the instructions as to how much to inject into any given size of tyre. Don't give it just another squirt to be on the safe side-you will probably suffer from imbalance problems if you do.

You must regularly inspect tyres for damage, nails, screws, etc because you will not get early warning of punctures by means of the tyre deflating.

Despite dire warnings from the tyre industry that the stuff damages tyres rendering them not repairable, the one time I had a puncture that needed repairing the stuff just washed away with water and the tyre was repaired as normal.

On the whole, good stuff.

NB -There are now two sources of Ultraseal, the USA or the UK, the UK stuff is made in Exeter.