Should have been clearer, after something that can record multiple lap splits and although my Casio W86 has a split timer, I'm not sure it can hold more than one split.
Ah, I’d plump for something like a Forerunner 45 (or 55, or 735. Anything a generation or so old and entry-mid range). Should be able to find one for £50 or so on eBay in good nick.
Cheers @Rich_G and @duncs that's helpful.
Should have been clearer, after something that can record multiple lap splits and although my Casio W86 has a split timer, I'm not sure it can hold more than one split.