This was my favourite extract kit. Lovely and quaffable, and very straightforward to brew. Didn't last long at all.
You can make so much better ag though. I'd say start with a fairly neutral base (extra pale/Maris otter/golden promise, with perhaps 10% total oats/wheat malt), keep the boiling hops to a minimum and go big on the whirlpool hops (mosaic, citra, aiming for around 30 IBUs, I don't remember it being bitter). Then a nice three day dry hop and happy days.
Yeast depends on your preference. Could use the same mangrove jack one or go US-05 or similar.
If you are fiddling with the water, I'd say reduce alkalinity as far as possible, and go bigger on chloride than sulphate.