I've looked at u-blox, telit, Simcom and Quectel.
The best receiver from cold start I've found so far is from Telit at -148dBm for acquisition (cold start).
e.g. telit jupiter se868
Has anyone come across a GPS module with a better cold start sensitivity?
Cold Start is performed every time when the GPS module is turned off without backup power supply connected. It is the longest starting time out of the three and usually takes 35 seconds in average under open sky environment. During Cold Start, almanac and ephemeris data has to be downloaded first from the GPS satellites to GPS module before a position fix can be acquired.