125s are fine for commuting short distances. But 50 miles each way, with dual carriageway and motorway to boot, is a serious journey, and I'd have thought it's going to be a pretty miserable experience in the dead of winter unless you're on a significantly bigger machine, with a happy-go-lucky engine, heated grips, a headlamp that puts a searchlight to shame, and a decent, sod-off screen.
A Burgman 650 would be a super-sensible option, or else a Versys 600/650, or a Honda NC750X. Better still would be something that doesn't have a chain, like a BMW F800ST or an even an R1200GS (good grief, look what I'm doing here... ) - but the GS comes at a price of course. Of these, I'd suggest you have a serious look at the F800ST.
If you're looking for something to do the journey in spring, summer and autumn, then something smaller would do you, but for me, I'd still not want to flog a 125 hard up against the rev limiter for an hour each way 5 days a week.
So I'd say DAS is your one viable option.