Try:
UK AIP GEN 1.7 - Differences from ICAO Standards, Recommended Practices and Procedures
DOC 8168: Procedures for Air Navigation Services - Aircraft Operations Volume II (Construction of Visual and Instrument Flight Procedures) (4th Edition)
Part III Chapter 1
1.9.2 Procedure Speed Restrictions. Unless otherwise stated, procedures are speed restricted to a maximum IAS of 185 kt.
Part III Chapter 7
7.3.2 Turn Paramters - IAS. Unless otherwise specified, all missed approach turns are limited to 185 kt IAS maximum.
This is not a speed category specific limitation. I once asked someone in my company's performance dept. and there was an explanation as to why we weren't speed limited to 185kts in operation. I think it was along the lines that each approach procedure was individually checked out for each aircraft type using that type's SOPs and speed / perf characteristics and so the "generic" restriction of 7.3.2 didn't apply. The legal framework for that is probably buried within the AOC. Or else the "unless otherwise stated" bit - anyhow the CAA FOIs seem happy with it (for all UK airlines...).
HTH.