The one-liner responses so far are a little confusing. There are a several of points to consider:
1) In Class A Airspace in the UK there is no 'blanket restriction of 250 kts below FL100'. There are speed limits based upon certain criteria, such as the need to ensure one departure does not catch another on the same route, or to ensure that traffic running into the holding fix is not doing 300kts and taking up the whole sky as it turns into the hold.
2) Broadly speaking, there are arrival and departure speed restrictions. On departure, there is an automatic speed restriction of 250kts MAX. This is to prevent the 757 hoovering the A340 ahead until the radar controller can provide another form of separation. To have the speed restriction lifted does not mean you HAVE to accelerate. Indeed, if by doing so you will be unable to make SID or enroute level restrictions then you should not do so. All it means is that ATC have no reason to restrict your speed.
3) Arrival restrictions may take to form of SLP (Speed Limit Points) which are marked on the Arrival charts. For example, you are expected to be 250kts by 12 nm before LAM into Heathrow. This is to allow both reasonable sequencing if appropriate or to ensure you stay within the holding area.
So, in Class A in the UK, provided you can make touchdown speed at the threshold you can, with ATC's permission, do 340kts all the way down to final if you wish.
As an aside, ATC cannot 'approve' speeds above 250kts below FL 100 in Class G, as it is a national speed restriction and has important benefits in the 'see and avoid' principle.