There is a choice of Polypipe 160mm underground fittings available at Trading Depot. Among the 160mm Polypipe underground fittings is a double socket underground coupler, underground level invert reducer 160mm to 110mm, and a rodding eye oval top / socket tail.
Also available is a Polypipe 45 degree double socket bend, 45 degree triple socket equal tee, 87.5 degree double and single socket bends, plus an 87.5 degree triple socket equal tee.