Reg.92 of the Public Contracts Regulations 2015 (PCR2015) establishes the general time limits for starting proceedings to seek remedies other than ineffectiveness derived from breaches of Part 2 PCR2015 or EU actionable procurement rules [time limits for proceedings seeking ineffectiveness are established in reg.93 PCR2015].
In general, and in a simplified manner, proceedings must be started within 30 days beginning with the date when the economic operator first knew or ought to have known that grounds for starting the proceedings had arisen [reg.92(2)]. However, the Court may extend the time limits imposed where it considers that there is a good reason for doing so [reg.92(4)], but it must not exercise that power under so as to permit proceedings to be started more than 3 months after the date when the economic operator first knew or ought to have known that grounds for starting the proceedings had arisen [reg.92(5) PCR2015].
For discussion on the calculation of these time limits, see R Ashmore "Curing the "incurable"? The possibility of serving a technically defective claim form "out of time" as recognised in Heron Bros Limited v Central Bedfordshire Council" (2014) 23(4) Public Procurement Law Review NA134-NA139. Even if the case discussed was Irish (and hence subjected to different rules), the issue of knowledge in relation to time limits for bringing proceedings is addressed in an interesting way by P McGovern, "Application of the principle of transparency in stating criteria, and application of the concept of knowledge in relation to time limits for bringing proceedings: the case of Gaswise Limited v Dublin City Council" (2014) 23(5) Public Procurement Law Review NA145-NA148.