An update on this for future reference in the event that anyone has a similar query.
The matching alloy arrived from the eBay seller quickly and is in great condition - no curbing marks etc. The tyre fitted looks nearly new. It fits in the spare wheel well no problem and i have secured it with a genuine Honda clamp. The design of the clamp means that the wheel will only fit one way - which is fine - as mentioned in a previous post when the wheel is stored this way you can keep store other things inside it.
I bought a new 2 ton scissor jack and was pleased to find that there was enough room to slot it into the wheel well just below the warning triangle compartment. Bonus!
Its also possible to fit a few things in the floor hatch cargo net too - in this case a spare bulb kit and fluorescent jacket.
With all of that tucked neatly away I fitted my new plastic boot liner:
For everything else that cant be slotted in like a small selection of tools along with spare clothing and other emergency supplies - these all fit in two small black nylon bags.
I hope thats all helpful to someone!