Apologies again for another off-topic reply!
Additionally, mixing HPS into LPS streets is an outrage and something my borough council started doing in 2004 up until when the PFI started in 2006 in which they started using spare LPS lanterns again.I must admit that Essex's decision to install SON even for casual replacements is probably not as bad as it sounds. For a start, the colour of SON seems to be much more 'yellow' these days compared to about 30 years ago, when they were almost pink, so where the first few SON P567s and SGS203s have appeared in previously SOX-lit streets, the change in colour is not as stark as it would have been if Essex had decided to move over to white light instead.
In fact the difference in colour is not as stark as the last time Essex decided to change light sources; from MBF to SOX in the 1970s. Almost 40 years later, and the slow-paced change from MBF to SOX in Clacton was around two-thirds complete before this new change over to SON.
I'm surprised the replacement lanterns are not of the modern post-2000 variety...the SGS203s are now old technology however cheap they may be.I'm guessing Essex has always been 'behind the curve' when it comes to innovations in street lighting! In the 1990s and 2000s, the most widely-installed lanterns by a country mile were Philips XGS103/XGS104s and SRS201s, both arguably old technology in both of those decades and definitely in the latter. In fact their stubbornness with the XGS103/XGS104s and SRS201s for the last two decades has actually returned lantern uniformity into streets which hadn't seen such lantern uniformity since the original lighting was installed in the 1950s and 1960s! In those small pockets where Essex has installed SON in the past, they have gone for the '203 on both main roads and side roads, so I'm not too surprised that Essex think that installing SGS203s in SOX-lit main roads will eventually result in lantern uniformity in, say, 20 years from now!