Strange how you feel on cars, you get invested and feel something is hard to let go, but once made the decision, other car is not in sight, and in something else appreciate, you soon move on, and in your case, the extra ££ will look nice in the account and your driving experience is still a fulfilling one, and looking at TCR prices, they are still holding strong.
It would have cost me £16k extra to keep the TCR as second car, that money now looks better in the bank.
I could imagine you getting over the initial newness of the MK 8, seeing a TCR and having huge doubts, so 100% best decision.