Haha… you come on here to ask about trousers to mountainbike in and 10 merry middle aged men will turn up to tell you all about their ladies hosiery.
I have tons of pairs of riding trousers ranging from full motocross cordura DH pants through to lighter weight DH pants to water repellent and thinner trail trousers unfortunately very few of them are the current year model and many are no longer in production.
For lighter weight trousers that are fairly durable check out the ranges from Endura, Madison and Scott, slighlty heavier weight Dakine and ION and for properly durable check out race pants from the likes of Fox, Troylee, TSG etc. The Boardman’s mentioned earlier aren’t a bad shout for £50. Polaris also do a cheap pair but styling is questionable.