Given that I can only have one antenna and it has to be a single
vertical, not exceeding 45 feet, I'm seeking advice on the best way to
achieve this.

The feed point must be at at ground level and will be 100 Metres away
fed with low loss coaxial cable.

I can lay down a good radial system and ground rod at the feed point.

I'd like to use the antenna on all HF bands, or as many as possible
from 1.8 MHz up.

My choices seem to be,

1. A commercial HF Multiband antenna eg, HF9V
or
2. A vertical wire supported by a 40'-45' fiberglass pole with an auto
ATU at the base, eg SG230.

Q . Which way to go? Naturally I'd like to achieve some low angle
radiation on some bands.

I'd appreciate any advice on which would be the most efficient system
given my constraints.

Anything else I haven't thought of ?

73, F5VJC