He added that his wife, a lawyer for mining firm Anglo American, "was a wonderful, perfect wife and a brilliant, loving and inspirational mother to our two wonderful children".
"Alex and Annabel were the most amazing, intelligent, talented and thoughtful children, and Anita and I were immensely proud of them both and looking forward to seeing them develop into adulthood.
"They shared with their mother the priceless ability to light up any room they entered and bring joy to the lives of all they came into contact with."
He thanked the medical teams in Colombo and the Sri Lankan people he had encountered since.
Assistant County Fire Officer Dave Keelan, of Greater Manchester Fire and Rescue Service, has paid tribute to his former colleague Mr Harrop after hearing the "devastating" news.
"Bill served here for 30 years, retiring at the end of 2012. He was a much a loved and respected colleague and friend. He will be greatly missed."
It is not currently known which explosion killed the couple.
Most of those killed in the explosions are thought to be Sri Lankan nationals but officials say at least 31 foreigners are among the dead including British, Indian, Danish, Saudi, Chinese and Turkish nationals.
The UK's High Commissioner, James Dauris, confirmed that eight British citizens were known to have died but said there were no further Britons with serious injuries.
Mr Dauris said: "We know there are a small number of foreign nationals who are unaccounted for. We don't know what the nationality of those people is."
He urged those still in the country to contact relatives and to follow instructions from local authorities.
Manisha Gunasekera, Sri Lanka's High Commissioner, told the BBC that the large Sri Lankan community in the UK was "very concerned".
The Queen has offered her condolences to Sri Lanka's president, saying her thoughts and prayers were with all Sri Lankans.
She said: "Prince Philip and I were deeply saddened to learn of the attacks in Sri Lanka yesterday and send our condolences to the families and friends of those who have lost their lives."
Three churches in Negombo, Batticaloa and Colombo's Kochchikade district were targeted during Easter services. Blasts also rocked the Shangri-La, Kingsbury and Cinnamon Grand hotels in the country's capital.
Police then carried out raids on two addresses and there were explosions at both. One was in Dehiwala, southern Colombo, and the other was near the Colombo district of Dematagoda in which three officers were killed.