As a quick update (which may or may not help others!) I ended up cancelling with Audi and reinsuring with them to kick this out another year within their expiry dates (which means I can hopefully also sort issues with my NCD out too!).
Adrian Flux were well over £2k, eSure and Audi v similar around £1500. Interestingly the front end for UKI is Churchill and Directline, neither of which will underwrite performance cars!