I used to ride XC in trainers, but enough stones stubbing my toes I've being using mywalking/ascent shoes.

 I've finally decided to buy some trainers for XC/downhill (ish)

 After my last 25mile ride around Jacobs Ladder, Kinder, Castleton etc. I  think i need

Good grip, solid toe, some waterproofness maybe

I was looking at some 5.10's as I climb, but not sure if they are not more jump trainers than XC/DH getting wet and dirty with each ride.

Any advice please.

I've not moved as far a grown up pedels yet.

 I still like to be down with the kids and ride with flat pedals.

Also like to wear my clothes back to front like tick tock, but that's probably showing my age too much...

5.10's are very good, along with DMR V12's, but for XC you do want to be riding in SPD's.

I regularly swap between SPD's and flats, depending on what I'm doing - but always use SPD's for XC.

I looked at some 5.10's yesterday.

 They just seemed like chunky DC's. 

 For £75 they seem a bit too nice to be getting wet and muddy every weekend.

You'd hope for that money they'd be a bit more tougher with rubber on the toes, or with gore-tex.

A little too expensive for what they are and what they would be used for.

If I knew what DC's were...

5.10's are very strong, and have a very good rep. because of it.

And TBH you won't get decent shoes and gore-tex for that kind of money - but seriously, for XC go SPD - you'll get a pair of basic shoes and pedals for £75 - like these:

http://www.merlincycles.co.uk/mountain-bike-shoes/shimano-mt41.html

http://www.merlincycles.co.uk/mountain-bike-pedals/shimano-bike-pedals/shimano-m520-spd-pedal.html

Also Shimano shoes come up real small, so you really need to try them.

Or if you are prepared to spend more, and want good protection plus gore-tex, I've some of these, and they are superb:

http://www.merlincycles.co.uk/mountain-bike-shoes/shimano-mt90l.html