If you're looking for lightweight cabs, and in England, Barefaced might be worth a shot.
At £520 the Two10 should handle your head output. It's relatively small and an easy carry. The only issue is it comes in 4 or 12 ohm wiring. If one is enough, a 4 ohm would be ideal. If you're crew is silly loud a second one would be needed, so a 12 ohm would be a better option. If you're getting by on your 115, the single 4ohm 210 could do the job. I've owned one, and it is very nice and light.
For £569, you could step up to the Super Compact, which is similar in output to the 210, but voiced a little differently. It will take the output from the head you've got, and it's a silly light one-handed carry. If you don't need massive low end extension not the tweeter of their BB2 cab, then it's a great combination of size, weight, and output. It will most likely be a big step up from your current 115. I only sold mine to move up to the BB2 from them, because I use it as a full-range PA style monitor, for some gigs. The Super Compact is an 8ohm cab, so you could add a second one for a 4ohm rig which would be silly loud.
In my experience, the bulky lugging is the hardest. Downsizing to a smaller, lighter cab might be beneficial to your lugging.
You also get a one-month trial/return period on your side of The Atlantic.