Disclaimer: I don't know what the custom is in the UK.
As far as I remember, any speed/altitude restriction on a SID must be explicitly cancelled by ATC ("no altitude/speed restriction [at/after/to FIX]"). I think it's in ICAO doc 4444 but I wouldn't put my finger on it.
(Also, why would you think that a clearance to a higher level would cancel a speed restriction? I'm actually interested from my ATCO-only point of view)
As for the "climb now", although I've heard it mentioned on the web from time to time, I don't believe is standard at all and honestly I think there are a few different ideas of what it means, depending on the ATCO/Pilot you ask.