And Quins' bad night was complete when prop Louie McCarthy-Scarsbrook went off with a broken wrist.
Quins' slim half-time lead soon evaporated as Hemingway added another penalty in the 44th minute.
Crusaders skipper Van Dijk hopes to be back for the Brewery Field clash against Quins.
But they missed several chances before Chris Melling slid over for Quins with five minutes remaining.
Joe Marler added a late try for Quins, but it was too little, too late.
Irish soon established control, however, with Bachop sending tumbling kicks deep into Quins' territory.
However, Randall dummied the defence to go over from close range to ease Quins' nerves.
Skipper Rob Purdham was the key as Quins came back brilliantly after Catalans' bright start.
Nick Evans added a second penalty but Quins did not score in the second half.
Quins will not be taking up the option to extend his contract beyond May 2005.
BBC: SPORT | Rugby Union | English | Injury forces Cronje out of Quins
Quins piled on the pressure but could only muster a try from Danny Care.
Nick Easter scored Quins' first-half try to earn the home side a 16-6 lead.
The Llanelli side face a testing trip to Stade Francais next week, while Quins host Ulster.
Danny Care's score gave Quins hope but Hart's 74th-minute try settled the tie, before Strettle's late consolation.
As Quins desperately sought a score before the interval, scrum-half Danny Care pulled a drop-goal attempt wide.
Quins also crossed twice, through Hal Luscombe and Mike Brown, but the visitors were always playing catch-up.
But immediately from Evans' restart, Quins scrum-half Danny Care picked out Camacho with a perfectly weighted cross-kick.
Mark van Gisbergen's third penalty extended it before Wasps ended Quins' resistance with a late penalty try.
Evans converted to narrow the gap to five points and a revitalised Quins built up sustained pressure.
The Sharks had been in Quins' 22 just once before their first try in the 26th minute.
Quins went ahead after Danny Orr's clever kick through was gathered by Matt Gardner on 11 minutes.
Monday night's match with Quins also saw the first appearance in a Wasps shirt of rugby league convert Lee Smith.
The Exiles feature England Sevens players Paul Sackey and Geoff Appleford, while Quins include exciting wing Ugo Monye.
Quins hit back two minutes later when some slick handling culminated in Chad Randall sending Tony Clubb over.
Meanwhile, Quins chief executive Mark Evans says the club are undecided as to whether they will replace Richards.
The Rugby Football Union has confirmed that former Quins physio Steph Brennan, now with England, has been suspended.
Jamie O'Callaghan crossed for Quins but David Williams, Brett Stewart, Jamie Lyon and Steve Matai sealed the win.
The former Wales Under-19 international arrives at Quins from Newport Dragons, where he was on loan from Bath.
But the Quins winger let the ball slip out from underneath him, presenting Simpson with the easiest of scores.
And, within three minutes, he had added another, claiming a high kick as a ragged Quins defence stood watching.
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