Where the relevant authority (the Highways Agency, the County Council or Unitary Authority) has made a notice, under Section 14 of the Road Traffic Regulations 1984, restricting the speed of vehicles through roadworks, it is an offence (under Section 16 of the Regulations) to fail to comply with the speed restriction.
Otherwise it would appear that simply exceeding the temporary speed limit is not, per se, an offence. However a police officer might still take the view that driving in a way which could lead to chips flying into the air (endangering pedestrians, cyclists and others) constituted 'driving without reasonable consideration for other persons', contrary to Section 3 of the Road Traffic Act 1988:
http://www.cps.gov.uk...s_of_bad_driving/#a16
Chris