undertheweather
You have raised lots of interesting questions, that are sort of interelated, especially with the Channel Islands aspect.
Firstly, I would strongly suggest that you get advise from your own accountant, BEFORE, you buy a company. Getting expenditure relating to aircraft & flying, allowable for VAT & tax, is notoriously difficult, & should be planned before you buy the aircraft.
(Note to Big Red "L" .... I am not touting for business .... I am far too busy!)
And undertheweather, do not hire an accountant who is prepared to barter flying for accounts. Firstly this is known in my trade as "conspiracy to defraud the public revenue" & secondly, it is difficult to sue that accountant for bad advise, if you suggested this arrangment
The main reason for using a company to own a light aircraft, is to cover the uninsured part of third party claims. If you are sued for billions, then you just put the company into liquidation. Nowadays there is far less tax advantage, in a limited company, unless you are going to use the aircraft for a real business use.
As to whether you should buy a Channel Islands company, this is definitely one for your accountant, as he would have to take into account all other aspects of your finances, for proper tax planning.
One point to be very careful of, is the current VAT status of the aircraft. The CAA's UK register of G reg aircraft does cover the Channel Islands, so I assume that you are buying a G Reg A/c. However, the Channel Islands are NOT part of the UK for tax or VAT. Furthermore the CIs are outside the EU, for VAT purposes.
This can mean that VAT may or may not have been paid when the aircraft was first inported into the UK. If it went straight to the CIs & stayed there, & was not imported into mainland UK, then VAT may not have been paid. If so, if you are intending to keep it in mainland UK, then you will have to complete its importation and pay over the VAT. If the aircraft, has been registered in the CIs but has been keep in mainland UK, for more than 6 months, then VAT should have been paid. Prove of its VAT status, is either a UK Customs & Excise Form C88, or otherwise you need a letter from UK C & E confirming that the aircraft "is in free circulation in the EU" (In Customs-speak this means that VAT was paid on import). There are various other complications that can occur on VAT, such as was the existing CI company operating the aircraft in mainland UK, so might be VAT registered?
Please bear in mind, that unless your company does genuinely intend to trade, it may have difficulties in recovering any VAT paid on the aircraft, or on subsequent aircraft maintenance etc (this is another point for your accountant)
This leads on to the Public C of A question. From your posting, I asume that it is on Private C of A at present. If so, you need to talk to an aircraft engineer, as the costs of upgrades from Private to Public C of A, seem to vary from very little, to astronomic! If you are getting an engineer to survey the aircraft before you buy it (which is usually a good idea) he may be able to give you a rough idea of the costs.
As regards registering the aircraft at your home address, this will depend on whether you are going to buy the CI company, form a UK company, or own the aircraft personally. Clearly if you register the aircraft to an address in mainland UK, you would have to ensure that it has been legally imported for VAT purpose, as mentioned above. Also the aircraft owner in the CAA register should be the limited company, if you are using one, & not your personal name. Otherwise this might invalidate the original reason for the limited company .... to cap any third party claim, & could conteract any VAT or tax advantage.
It is very difficult to give you complete & concise answers on this subject, without the full facts, & I have rabbited on enough, already
If you have any further queries, please post them here & I will see if I can answer them.