I was describing this problem to the guys in #Helpdesk at the weekend - not sure if you were there

I did a little research into what irssi responds with when you re-connect to it, and the names raws are in there. However, they appear to be out of sequence compared to a join from a normal server:
mIRC-initiated JOIN sequence:
-> Surrey.UK.EU.Undernet.Org JOIN #mirc
<- :Proboscis!~wibble@host<removed>.btcentralplus.com JOIN #mIRC
-> Surrey.UK.EU.Undernet.Org MODE #mIRC
<- :Surrey.UK.EU.Undernet.Org 332 Proboscis #mIRC :mIRC 6.14 --> http://www.mirc.co.uk/get.html -- No lameness - No flooding - No msg'ing the ops - No bot questions - No aways!
<- :Surrey.UK.EU.Undernet.Org 333 Proboscis #mIRC mIRC- 1085070211
<- :Surrey.UK.EU.Undernet.Org 353 Proboscis = #mIRC :Proboscis Kozani_30 Pepsi-Cola @Julie2 raffy ScoT NetDevil is`OUT RAPTOR_BM ncdpuy NoNaMe^^^ daniel789 CHETOS rmngdq Mentality TiuDu init`OFF Eistee deGi Ramo22 road^bump mirrian @Sais MyAnGels SteInMetz Scarab BEAR33 Scat-Man @prescott dwkdj niceone Dennyy- martyanu- DotBlue_ Kniht gdrAW sirmokiem racefan Segosa IceShaman [R]ick Sigh_ Rockj p-stats Diabolique Raccoon BrEaKaBlE Mike` tolecnal spooki Kedishen Maghaweer Jagfire @WOT MadRomeo
<- :Surrey.UK.EU.Undernet.Org 353 Proboscis = #mIRC :@magic @childofchaos @mIRC- Loagan Rydekull csian @mERK @X Salomonis
<- :Surrey.UK.EU.Undernet.Org 366 Proboscis #mIRC :End of /NAMES list.
<- :Surrey.UK.EU.Undernet.Org 324 Proboscis #mIRC +tnl 69
<- :Surrey.UK.EU.Undernet.Org 329 Proboscis #mIRC 823923645
irssi-initiated (re)JOIN sequence:
<- :Sais!mnj@proxy JOIN #mIRC
-> undernet.proxy MODE #mIRC
<- :undernet.proxy 353 Sais = #mIRC :dwkdj SteInMetz sirmokiem spooki @mERK mirrian @magic Raccoon @prescott Diabolique BEAR33 Loagan Kedishen Scarab Mentality DotBlue_ Scat-Man init`OFF ncdpuy ScoT CHETOS @Julie2 Mike` @WOT Rydekull @X Salomonis road^bump is`OUT MyAnGels martyanu- RAPTOR_BM NetDevil Sigh_ MadRomeo Rockj Eistee rmngdq Kniht IceShaman [R]ick TiuDu @mIRC- Dennyy- Ramo22 raffy racefan niceone NoNaMe^^^ daniel789 Pepsi-Cola @childofchaos BrEaKaBlE Jagfire tolecnal gdrAW @Sais Maghaweer
<- :undernet.proxy 353 Sais = #mIRC :deGi csian Segosa p-stats
<- :undernet.proxy 366 Sais #mIRC :End of /NAMES list.
<- :undernet.proxy 332 Sais #mIRC :mIRC 6.14 --> http://www.mirc.co.uk/get.html -- No lameness - No flooding - No msg'ing the ops - No bot questions - No aways!
...
<- :Surrey.UK.EU.Undernet.Org 324 Sais #mIRC +tnl 66
<- :Surrey.UK.EU.Undernet.Org 329 Sais #mIRC 823923645
Note that the sequence in the first case is:
332, 333,
353 ... 366 ,324,329
while in the second case, the names come first:
353 ... 366, 332, 324, 329
(hmm. and missing 333 RPL_TOPICWHOTIME)
Question: does the order matter? I don't *think* it's specified in RFC 1459 (I'll check and ammend this if I find out).
I'll also play with the irssi proxy, and see if I can recompile it to send the replies back in the first order - I think it's easy-ish - see if that has any effect.
As for the network recognition problem, I'm not sure how mIRC recognises the network name, it doesn't always seem to update when I use /version. I suppose you could hack irssi to generate a 005 response with the group name...