Yes on the windlass in Channel Islands. Anchorages are pretty deep.
I agree with Nomad Willy that no heroic measures needed for the battery bank - use your existing bank (assumes decent condition) but obviously, keep engine running (which is normal anyway). Given you're a small boat, not a big deal, but (and you may know this but bears repeating just in case), best practice is to
not drag your boat forward with windlass but rather bump in forward gear and use the windlass to take-up slack in rode. When you are right over the anchor, bring the rode taut, then pause to give the anchor a chance to wiggle itself loose - rinse/repeat until free.
I have an old Ideal and I believe it is wired for 150A (3x50A breakers on the panel, which is not cool and is being replaced in my current refit). Shaefer Marine now owns Ideal - they show a 150A breaker on their webpage
HERE. Or you can get the BlueSea 150A one
SHOWN HERE
Here's the Blue Sea wire size chart. Note, 12-feet run is a 24-feet circuit. Looks like you are right on the line of 0 and 2/0 for 3% loss. I know this stuff gets expensive, but 2/0 might be your best bet unless the price difference is high.
Good luck - and congrat's on your new boat.
Peter