R&R will not use anything other than Porsche-supplied new parts. So using used parts with them is out of the question.
The guide insurers generally use for a total loss is if repair costs hit around 55-65% of the car's valuation they will declare it a total loss. You are on the edge of the lower limit of that figure (£30k repair v £55k value).
You can remove the car from R&R and explore elsewhere - after paying R&R's charges for the investigation and liaison they have done so far and preparing the assessment of damages report for the insurer - you will need to pay it as it is unlikely to be paid by the insurer if you are not having the car repaired by R&R. The insurer will only pay one charge from whoever you do decide to have it repaired with - whether its a total loss or they agree to authorize repairs - they will pay that repairer all fees minus your excess.
IF you decide to accept a total loss, unless you have a specialist policy with the likes of Locktons, the car becomes the property of the insurer.
So the scenario that you might be able to take the total loss value and then have it repaired from own pocket goes out the window.
If you have a Lockton-type (specialist) policy you could take the crash damaged vehicle in exchange for a 10% reduction in the agreed or market valuation of the car being paid out to you. If its not got such a clause in the event of a total loss, the scrap car becomes the property of the insurer to dispose off. If you know who they sell it to, you could take your total loss payment and then buy it back from the purchaser + his mark-up on the purchase price (he's never going to sell it back to you at the price he paid for it). Alternatively, you could commission him to repair it and use the total loss payment to buy the repaired vehicle back from him - but the total loss status will be registered at DVLA - a consideration when you come to sell it.
Agreed valuation carries a risk if the valuation falls or rises. If it falls, you are quids in as there is no dispute - contractually they cannot lower the total loss payment arguing that prices have gone down and the cost to put you back to where you were prior to the loss is less than the agreed value.
Conversely, you will not be able to argue that to put you back to where you were prior to the loss requires more than that agreed valuation. That's the nature of the beast I'm afraid. So I think the total loss payment will not exceed the agreed valuation.
In hindsight there may be grounds to have opted for "market valuation" and submit examples of replacement cars at higher price than what they are considering as the total loss value. But the wonder of hindsight is that it is a wonderful thing.
With the agreed valuation, one year I had to re-submit the valuation on my vehicle mid-year on a fast rising market to avoid being out-of-pocket in a rising market. Additionally, I have the valuation carried out annually (never leaving it for the validity of the 2 years that my
Insurance company gives).
I feel sad for the situation that you are in. Repairing it entirely out of pocket with a combination of used and new parts remains an option for you. But as its reported to the
Insurance, is there likely to be any trace of the severity of the damage prior to repair and what impact might that have on resale price when you come to dispose of the vehicle repaired with used parts?
Prima facie you might be looking at any range of options but anything that involves the current insurer points in the direction of a total loss. R&R can try to persuade them but in the end it is they, your insurer that decide whether to repair or write off.