To lower the gearing wouldn't be too difficult to do at home. I would suggest changing the rear sprocket first. It will be cheaper to do AND you'll learn what you need to do in the case of changing a flat and what it entails with the rear internal hub. Going to a 26 or 27 tooth rear sprocket would help you out quite a bit. I haven't done it yet so I don't know if you might need to add links for the chain or not or if there is enough room to move the wheel forward to give you more slack. You are on your own here for that part.
Sadly while doing a little research for you there only appears to be 2 sprockets for this hub, 23T and 25T. Looks like you could try the 25T and that would help you out a fair amount but not quite as much as I think you might need. It would give you the following gear inches:
109.4
85.4
75.3
66.7
58.8
52.0
45.9
35.9
This is a decent range but if you want lower you will have to go to a smaller front gear. I'd say change the rear and see if you can live with. If not then you are better just changing the front to something like a 37T or 39T. Hope this helps. I think the front chainring is a 110. It is either a 110 or a 130mm size. Most bike shops WILL stock these diameters and probably something close to the size you need. Keep in mind you will likely lose your chainguard.
I am personally going to try a 25T first and see how that works out. Should cost less and I'll keep the chainguard up front and that helps with chain issues. As a minor point IF you went the the smaller front ring you would shave a few grams instead of adding them. If you don't need the bar-ends you could ditch them too to save a little weight. Go with lighter brakes too and shave grams.
The pedals are hefty. Take them when you go pedal shopping at your loccal shop. They should have a scale. Weigh your potential replacements and see how they stack up.
Make sure that if you do order the rear sprocket that the normal SA sprockets will NOT work on the 8 speed!
FYI - here is the link to the manual for the SA 8spd hub.
http://www.sturmey-archer.com/pdfs/XRF8.pdf
I am not sure what size chain is on the bike but I found the 2 possible part numbers for the SA sprockets.
25T for 1/8” chain is 3202.0125.002
25T for 3/32” chain is 3202.0125.004
Hope this helps.