I thought Gatwick was a case in point as well, not just the right turns of 26L but the left turns off 08R as well.
On looking at the SID plates though, the only speed restriction mentioned is not above 250kts below 10,000ft.
A couple of examples....
<a href="http://www.ais.org.uk/uk_aip/pdf/ad/32KK0601.pdf" target="_blank">LAM SID</a>
<a href="http://www.ais.org.uk/uk_aip/pdf/ad/32KK0605.pdf" target="_blank">KEN SID</a>
WF.