* STOXX 600 up 0.3 pct, monthly gain of 1.8 pct
* Eurozone Q3 GDP data better than expected
* Spain's IBEX posts best performance since May
* BP jumps after Q3 results, share buy-back
* Earnings boost Ryanair, Croda, SCA
* BNP Paribas FICC trading disappoints (Adds closing price)
LONDON, Oct 31 (Reuters) - European stocks held at five-month highs on Tuesday, ending October with a 1.8 percent monthly gain, the second in a row, as third-quarter data fuelled confidence in the resilience of equity markets.
The pan-European STOXX 600 index closed 0.4 percent with most bourses and sectors ending in positive territory as fresh data showed the euro zone grew faster than expected last quarter and unemployment fell to its lowest in almost nine years.
"This morning's euro zone data provided a foundation on which euro zone equities have built small gains," IG chief market analyst Chris Beauchamp commented. He noted however that with Germany's Bourse closed on a bank holiday, "there is a feeling that investors are going through the motions".
Spain's IBEX posted its best monthly performance since May and closed the day 0.7 percent higher after Catalonia's ousted leader, Carles Puigdemont, agreed to a snap election called by Spain's central government to end the crisis created by the region's bid for independence.
Early trading was lifted by heavyweight oil major BP, whose shares jumped more than 3 percent to their highest level since July 2014 after its third-quarter profit beat expectations and it announced a share buy-back programme. .
"We were expecting this to begin some time in 2018 and today's announcement is a very positive surprise," UBS analysts said in a note. BP shares closed 1.7 percent higher and the energy index was up 0.8 percent.
The sector has struggled in 2017 and is still down very slightly in the year to date but analysts at Barclays believe the perception of investors could soon change.
"With the energy sector offering close to the highest premium of dividends to the market for nearly 30 years, this should in turn lead to a re-rating," the UBS analysts said.
Ryanair results were also well-received. The budget airline's shares were up 6.9 percent after it maintained its full-year profit guidance despite its public relations debacle over flight cancellations.
Chemicals maker Croda gained 4.2 percent after a trading update. Swedish forest products company Svenska Cellulosa jumped 2.3 percent after beating expectations .
BNP Paribas lost the most among banks, falling 2.7 percent after its results showed a disappointing performance in its markets business.
Swiss toilet and plumbing supplies maker Geberit sustained heavy losses, falling 4.5 percent after third-quarter sales and earnings missed expectations.
Barclays and Deutsche Bank have also struggled, with volatility low and interest rates at record lows.
"This is very much industry-wide, and it is down predominantly to the low volatility that we're seeing in the markets," said Jonathan Roy, advisory investment manager at Charles Hanover Investments. "These trading operations are starting to feel the pinch."
So far, 45 percent of MSCI Europe companies have reported results for the third quarter, of which 66 percent have either beaten or met expectations, according to Thomson Reuters I/B/E/S data. Financials and tech are sectors stand out for their large proportion of beats.
(Reporting by Kit Rees and Julien Ponthus; editing by Sujata Rao, Larry King)