Next best option would be direct from Steam @ £13.99. Alternatively you could grab it from Epic for £7.49 using the Rocket League voucher.
It's still on sale on Steam for £13.99 for the base game and the gold edition is £18.69 for the next 3.5 hours.
I don't trust this company asking for PII after they took the money. Any other vendors seen with this price?