Thanks.
I should have said, no tripod. I don't expect (but don't know for sure) that anything will be moving. I'm presuming it is all static.
Both the 18-55 and the 18-135 have OIS, so hopefully I can handhold at lower shutter speeds.
Personally I’d take the 18-55 as I’d be surprised if you needed anything longer (actually I’d take the 16mm F1.4 if I really had the choice), the 18-55 is just smaller, more discrete, an extended 18-135 with hood will draw attention!!
Thanks.
I hadn't thought of using the electronic shutter, I've never used it before! But it makes sense in a museum.
The only reason I've considered the 18-55 is that it's smaller and lighter and (I think) slightly sharper than the 18-135.
Thanks for the advice - much appreciated.