Glad you got sorted for somewhere to stay - for grandstand tickets you could try here:

https://www.stubhub.co.uk/find/s/?q=tt

Also tickets sometimes comes up on eBay

If not there are hundreds of great spectator spots around the circuit which you don't need tickets for - my favourite is the Bungalow, especially if the weather is good. That said, a day in the grandstand is still very nice.