I take it the slippage happens at the back? Quite often this is down to the cassette so check the sprockets that the slippage occurs in for wear/damage. If possible borrow another wheel and test on your bike, if the slippage still occurs check your chain to see if its stretched, alignment of the derailleur and that the hanger isn't bent. Also check your jockey wheels for excessive wear.
After 500mi and in most cases the drivetrain shouldn't need replacing no, one of the parts could just be a dud.
Sorry, yes, slippage always occurs at the back on the cassette. I was thinking about buying a new cassette and seeing if that solves the problem. Don't know wether to buy identical cassette or a better version of the same 11/36 set up.
No chance of me borrowing a wheel as my buddies are roadies.
So if I replace the cassette and it's still slipping should I replace the chain next? Alignment and derailleur should be ok as the LBS gave it a good service and said it shifted perfect - on the stand.
I'm not confident in the mechanic though. He told me 100% that a certain front chain set would not be compatible with my road bike. I took it to Evans and they fitted it and it shifts flawlessly.
Just wondering whether to see if the Evans mechanic can identify the problem before I start spending money replacing parts.
Thanks for the response.