Wray, who has spent many of his 29 years at Turner & Townsend building up its South African business, said the changes were intended to freshen up the firm.
"It's a bit like a Cabinet reshuffle," he said.
The changes at the 650-strong, £32m turnover consultant are:
Project management chief Bill Woolgar, management systems managing director Alex Amos and Turner & Townsend UK managing director Alistair Wilson remain in their posts.
Wray said he hoped a young QS team led by Clancy could extend expertise gained on central London commercial projects to schemes all over the UK.
Turner & Townsend has traditionally worked on industrial and inward investment projects, but with these fields of work looking unreliable, Wray wants to increase office building work, airport projects and work for Railtrack. Turner & Townsend is now likely to spend less time chasing retail business.
Wray said he wanted international boss Harrison to target two or three international markets, whereas predecessor Hewitt had tended to aim for work across a wider field.
Wray now wants to target the Far East and the former Eastern Bloc and wants international work, which currently accounts for 25% of business, to increase significantly.
The firm is looking to make acquisitions abroad, and Wray is keen to increase Turner & Townsend's involvement in the booming Irish market, possibly by buying another firm.
Turner & Townsend has prospered through private finance initiative work, particularly in light rail, and Wray predicts that this will continue.
He says: "I've watched the development of PFI from afar and internationally people are starting to dabble in it now. They are saying 'what can we do through this?'."
Wray also expects Hewitt to double or treble contract services business.
I forecast that within one year of the sale of our UK FM business, we will be back to where we were overall in terms of turnover and profitability
Wray said Turner & Townsend was keen to re-establish its facilities management expertise after selling this part of its business to Japanese bank Nomura last autumn.
The firm cannot start up a new FM business in the UK for three years, but Wray believes facilities management will be a growing trend abroad.
He said: "I forecast that within one year of the sale of our UK FM business, we will be back to where we were overall in terms of turnover and profitability."
But Turner & Townsend will be careful to avoid onerous terms. Wray said the UK FM arm had started to "run away with itself", with partners being asked to give 30-year guarantees on projects it was managing.
Although some QSs have predicted that IT costs may force two top five firms to merge, Wray said this would not suit Turner & Townsend.
WS Atkins approached Turner & Townsend before buying Faithful & Gould in the mid-1990s, but Wray said the firm was not keen to sell out.
From now on, Wray plans to spend most of his time in the UK. He went to South Africa in the early 1980s but is confident that he will get back into the UK market quickly.
He said: "I've never really lost touch with the individuals at Turner & Townsend or the client base. That said, I don't intend to become involved with individual projects in the UK. I don't think, in this day and age, I could afford the time."
South African market
He said the South African market had not changed dramatically since the end of apartheid because the fear of crime has kept a lot of international companies away.
And he insists that working in South Africa during apartheid was not a problem, maintaining that the political system was "not everything it was cracked up to be".
He said: "There was a time South Africa wasn't the place to be seen for a British practice.
"There is no doubt there was a stigma in the early days. It had to be the part of Turner & Townsend no one knew about, but we have a real niche here now."
Clients will always need QSs
Although new government procurement strategies are placing contractors as civil servants' key points of contact, Wray is confident that QSs will survive.
"The client will always need a representative, and despite any guidance to the contrary, most educated clients will continue to think that," he said.
He also believes that because there will always be confrontation in construction, there will always be a need for contractual advice. Clients moving into overseas markets would need particular help, he said.