Not all the SLPs in the UK are worded in the same way. Check out Heathrow, Stansted etc compared to Gatwick.
The wording you quote is used at Edinburgh.
My understanding is that if you cross the SLP above FL140 you can be above 250Kt.
That means that you will have to be at 250Kt at FL140 if this happens between the SLP (or 3minute to run point) and the hold entry fix.
Remember though that the holding speeds i.e. the speed you must be at as you enter the hold is 230Kt up to FL140 and 240Kt FL145 to FL200. So for example hitting TARTN at 300Kt is not going to bode well for a nice hold entry.
Having said all that, if you are going to have to hold and expect to enter a stack with a FL70 ish base above FL140, I would be more worried about slowing down early and working out the diversion options than racing in at high speed.
Regards,
DFC