LESS THAN REQUIRED WAKE TURBULENCE SEPARATION BETWEEN HEAVY WDB AND TRAILING MLG ON APCH. OPERATIONAL ERROR.

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WE WERE BEING VECTORED FOR A VISUAL APCH BEHIND A COMPANY WDB WHICH WAS TURNING FINAL AHEAD OF US. WE WERE TURNED ON FINAL 4 MI BEHIND THE HVY APPROX 7-8 MI FROM THE ARPT AT 5000'. WE HAD THE TFC AND THE ARPT BUT WERE RELUCTANT TO TAKE OVER VISUALLY BECAUSE WE CONTINUED TO CLOSE ON THE HVY AND WERE BECOMING VERY HIGH FOR LNDG. WE WERE CLRED TO 4000'; BUT WERE TOO CLOSE TO THE TFC. APCH MOVED THE TFC TO LAND ON THE INBND RWY; BUT DUE TO THE PREVAILING WINDS AND THE POS OF OUR ACFT (4000' AND 5 MI FROM THE RWY) I ELECTED TO GO BACK OUT. IN THE PROCESS OF HAVING SLOWED THE ACFT; DIRTIED IT UP (GEAR DOWN; LNDG FLAPS); I LOST 200' (TO 3800') IN THE 180 DEG TURN BACK TO N WHILE CLEANING UP THE ACFT. IT WAS A POOR HANDLING JOB ON SPACING; PUTTING US IN THE POS OF SLOWING THE ACFT TO A MINIMUM SPD WITH LESS THAN 4 MI SPACING AND BEING EXTREMELY HIGH ON FINAL. THE CTLR WANTED US TO TAKE A VISUAL AND EXTRICATE HIMSELF FROM THE SITUATION WHICH ADDED TO THE CONFUSION. A LITTLE MORE CONCENTRATION ON SPACING EARLIER IN THE APCH WOULD HAVE AVOIDED THIS POTENTIALLY HAZARDOUS SITUATION.