Interesting question Spiny,
I agree with Chownah and Reflection that all we have to work with is our experience, and speculation about whether or not there are external things, and/or how well can we know them are outside the scope of Buddha-Dhamma.
To me, any attempt to confirm or deny
that there is a "real world" misses the point. That most of us, in ordinary life, or in more technical areas such as science, use a working model that there is something out there, and that is what we are measuring or experiencing, and use language that builds in that assumption. We don't necessarily take it seriously, but we don't waste time thinking:
"I will go into the laboratory and measure the wavelength of this light that may or may not be real with this apparatus that also may or may not be real. And, by the way, my very concept of wavelength is built on the assumption of ..."
I sometimes see criticisms that so-an-so ancient or modern teacher is making unfounded ontological assumptions. I think that such criticisms often arise from taking the language and working model too seriously, and can swing wildly in the opposite, just as beside-the-point, direction.