Catalans managed to open the scoring when Thomas Bosc found Dureau, who in turn fed Farrar.
Skipper Rob Purdham was the key as Quins came back brilliantly after Catalans' bright start.
But Catalans, who entertain Warrington in the play-off eliminator on Saturday, would not lie down.
Basques and Catalans think themselves distinct nations, as, to a lesser extent, do Galicians.
The skirmish is the latest in the Catalans' long war to defend their language.
The Catalans have already won the Club World Cup, the European Supercup and the Spanish Supercup.
On Friday, Barcelona vice-president Ferran Soriano suggested the Catalans were close to signing the 24-year-old.
By choosing to take on Mr Rajoy right now, Catalans are playing with fire.
But it was all Catalans in the second half, with Casey McGuire's excellent try starting the fightback.
BBC: SPORT | Rugby League | My Club | Catalans Dragons 30-22 Leeds
Centre John Wilson extended Catalans' lead after the break, with Thomas Bosc adding the extras with the boot.
The next wobble could come in October or November, when Catalans vote in regional elections (see article).
Philip V abolished Barcelona's Cortes and imposed Castilian law on all parts of Aragon's crown, including the Catalans.
He has been trying to create a standard curriculum for Spanish history throughout Spain, even among Catalans and Basques.
But Lomax again failed to convert as Catalans held on with relative comfort.
But Catalans hit back to stun Saints with three tries in seven minutes.
His first game in rugby league is likely to be a Super League fixture against Catalans Dragons on 19 March.
Bradford are fourth-from-bottom of the Super League table with their only win so far coming away to the Catalans Dragons.
Ryan Hudson extended the home side's lead with a try after the break, but Catalans hit back with David Ferriol.
The polling evidence suggests that no more than a fifth of Catalans are remotely tempted by the idea of independence.
Whereas one-third of Catalans are convinced separatists, many others are simply enraged by their tax money propping up poorer regions.
Either way, it will heat up the atmosphere as Catalans prepare to vote for their own parliament in the autumn.
ECONOMIST: Catalonia is set to have a big role in Spain��s politics
For Catalans, Aragonese, Galicians and Basques, it was an amalgam of which Castile, the imperial centre, was just one part.
Mr Bosch says his task is to integrate 1m foreigners (one in every seven Catalans) who arrived in the past decade.
Bosc added the extras, becoming the first Catalans player to break the 300-point mark in the Super League in the process.
Catalans' victory maintained the sequence of teams doing the double in this fixture, having won 32-22 on Welsh territory in March.
The Catalans have an option of buying him back at the end of the season, but Crosas is focused on Celtic.
But the Catalans then responded with five tries until Wigan ran in a second try through Michael McIlorum just before the break.
Such divisions could undermine the anti-terrorism pact which all the country's main parties, including Basques and Catalans, have upheld for a decade.
But, he says, the Catalans (and Basques) want more, not less, autonomy.
But, as I walk through the twisting alleyways of Italy's capital, songs from both the mighty reds and the Catalans sweep past me.
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