I am considering this bidet toilet seat for my elderly mother.

Luxe Bidet MB210 Fresh and Hot Water Spray Non-Electric Bidet Toilet Seat Attachment
Amazon.com: Luxe Bidet MB210 Fresh and Hot Water Spray Non-Electric Bidet Toilet Seat Attachment: Home Improvement

Does anyone have any experience with toilet seat bidets that might help me make my purchase decision?

The hot water to the bathroom takes 30 sec to get warm with the faucet running on full. I was considering a thermostatic mixing valve but don't see how it would solve my problem as it cannot raise temperature of the water until the hot water makes it to the valve. Is this correct and is there a solution that would correct this?

 

I can't answer the bedet question but I have an Hand Grohe shower body which give me the desired temp almost immediately. They may have the same for a sink.