Whilst I welcome the extra funds, (however small) into Cornwall, I must say that I don't see the potential for an improvement in journeys from Par to Newquay. Yes a passing loop at Roche will enable an hourly service on the line, but it won't speed up the journeys, but an hourly service would be welcome. It's still going to take at least 1hr.45min for the return PAR-NQY-PAR. The bus service from Newquay to Par actually passes through St Austell and is far faster than the train service, given the two hourly service presently. Add the reversal at Par and the probable hold ups to the "Metro" service due to the up country delays on services from the far East, (London, Cardiff, Bristol, Exeter etc. XC doesn't give us any meaningful service in Cornwall anymore), it's not likely to be a very smooth operation.
I think the £50 million is a political gesture to try to keep the incumbent members for Truro and Falmouth and for St Austell and Newquay in their seats at the next General Election. Futile as it may be.
By the way, an after thought, there is a regular bus service already between the centre of Falmouth, via the centre of Truro, to the centre of Newquay, U1 and U1A which for oldies like myself is free, if you have the pass.