Get the flannel trousers done in the 16oz for sure...you will enjoy them as odd trousers with a sweater or odd jacket way more than the blazer jacket
I just had my tailor make up three 500-520gram woolen flannels (stone grey/brown, brown heather and navy) from Gorina and they feel absolutely wonderful...especially when paired with different fair isle sweaters or arran knit donegal cardigans