Investigators found evidence that Simmons purchased replacement cleaning supplies and bedding in an “attempt to conceal his crime.”
Det Supt Matt Webb said: “This was a callous and brutal murder that was clearly planned. He drugged his wife and then attacked her with a knife; she had no chance to defend herself.
“The overwhelming evidence against him left Simmonds with no option but to plead guilty.
“The impact of his actions that day will last throughout the lives of Tia’s family and friends.”
Simmonds also pleaded guilty to two counts of raping another woman.
For both these crimes he was sentenced to 12 years in prison.