I do not get a huge amount of
noise above this and the higher the freq the less noise I get

Hi MC-
The antenna sounds like a very nice compromise for your situation, and you're
better off than some folks I know. Getting a hundred or so feet of wire
outside, no matter how high, is a much better start toward better reception
than using an active antenna (which some folks have to use because they can't
even get ten feet of wire outside!) or other compromise system.
It sounds like it's working well for you, orthodox or not.
As for the noise, if you're living in an urban or otherwise electrically noisy
environment, you're going to find that noise in the lower bands, and there's
not much you can do about it immediately, or without other gear.
You CAN figure out a way to ground the antenna and the coax feedline to reduce
that noise considerably, and if it's really done right it may get rid of most
of the noise right off the bat, but this requires ground rods hammered into the
earth (having 'sole' use of the garden may allow this?) and ground lines/straps
to do it right. Search online and ask this room about low-noise grounding
systems for SW reception.
You can also purchase a noise-cancelling/phasing unit, such as the ANC-4 from
JPS or MFJ's 1026. These units take the input from TWO antennas (your main
antenna and a second auxilliary noise sampling antenna) and you then use the
unit to phase out the noise. Such units can also null an unwanted station on a
given frequency, so that you may hear a station you DO want on the same
frequency, so it can do two jobs for you!
I use one of these units and it works VERY well at removing hash and noise, but
takes some practice to use correctly. You'd also have to set up another antenna
to phase between and you may not have the same amount of room for a second
antenna. It would need to be seperated from the main antenna to some extent,
and should be able to hear the noise as well as the first antenna to really do
it right.
There's a LOT to get into when it comes to antenna grounds and noise-cancelling
gear, and I'm neither an expert nor have time to get into it all, hahah, but
I'm certain others in here have better advice and can lead you to some useful
sites for just this purpose.
Bottom line on the antenna though, get as much wire outside, as high and in the
open as you can, and safely away from power lines, and what works, works. Most
of us are lacking the full antenna land we want, so you build what you can and
go for it. Sounds like you've got a winner there!
Good luck-
Linus