There is a known fault on the gearbox of both engine sizes; the input shaft and main shaft bearings wear causing noisy transmission.Honda replace all four bearings routinely if this occurs at considerable cost (£800)-can be done for half the cost at independent specialists.I know this for a fact as my 03 plate has just had to have this done with less than 33,000 miles covered from new.This has occured at lesser mileages than this.Having said this I did not experience the problems you describe-sounds more like a synchromesh problem to me.Luckily mine was paid for by the supplying dealer but I would suggest finding a reputable specialist who will not fleece you.I live in Nottingham so could only recommend the chap I have dealt with who was recommended by one of the country's best gearbox refurbishers,Oakdenes of Nottingham.Sorry about the long response but these repairs are not cheap so sourcing good,reasonably priced alternatives to main dealers can save you buckets of your hard earned cash.Hope this helps,
Best wishes,
Craig James,
Nottingham.