I live in Southern CA and it will depend to on the weight of the flannel. However, summers are pretty much a no go as is much of the early parts of fall and late spring. The lighter flannels might be ok outside of summer time.
A few things to consider, since this isn't going to be an apples to apples comparison:
- The RLBL is a large, international retailer and has all the advantages that is offered by such an entity. KW is a small business, which might take a little time to respond to customer issues, but more likely to deliver a more personal experience.
- RLBL suits tend to be more contemporary with an eye towards current fashion trends, so you're going to see narrower lapels and a...
If the RTW pants are made to the same quality as the MTM pants you'd be in for a great value. The trousers that came with my MTM suit is very good quality and the cut is comfortable and aesthetically pleasing. One of my favorite pair of trousers. Of course if you truly want to have access to the nicer cloths there's no reason not to pay the extra for the MTM.
I'm a US 7.5D and haven't had too much trouble especially with the recent growth of quality shoe vendors on the internet (e.g. Leather Soul Hawaii, Skoaktiebolaget, etc...). I've also had some luck on the buy/sell here at SF as well as some of the ebay vendors.