Thanks guys.
Can't afford to worry about the tyre after the event - getting back on the road home would be the priority - unless anyone with experience can offer any sagely advice...?
Amazon are offering a neat little zip bag with a bottle of Slime and a pump at a good price. It just (only just) fits in the right-hand cavity under the boot liner so at least I now have some peace of mind - just hope it's not a false sense of security - but at least the customer reviews were very positive - some saying the repair was so good their tyre is still holding up months later...!