Measure the lobes with some calipers!

I wouldnt worry too much tho. Plenty of Rsi's have run hydros for years with no problems. The only issue being top end (and I mean the red line here) performance will be slightly down due to the hydraulic action, the gain being no more adjusting and smooth every day driving.

To be honest unless your building a "race" spec engine and plan to take it round to the max then, £600 odd on a set of mechanicals is really not worth it.

Despite what some say, the hydros will not damage the engine. If anything they will help preserve it as there is no risk of the valve timing being out.