In case anyone is interested in saddle bags, instead of panniers, I have some Ortlieb bags like these. Have not had chance to test them in the rain, but they are supposed to be 100% waterproof. They have no zips and roll closed at the top for anyone not familiar with Ortlieb stuff. They are fine at 70 mph.
Just thought some of you lot having to commute in the p,,,,ing rain might be interested.
( Iam currently serving licence suspension for speeding and use Ortlieb stuff on my pushbike as well).