The last planning application I did, i did it myself - with some help from the RSPB on bird survey (that was for a multiuser path in my day job) admittedly your problem may be credentials (I'm a ranger team leader which was good enough for our planners in east devon)
Consultancy can get very expensive very quickly so its best to gt several quotes and also to take up refferences etc - the reason i wound up doing our myself was the consultant we used originally writing silly crap like " as hedges are present it is reasonable to assume dormice are on site" - ah no , just no , thats like saying we have grasslands so we must have buffalo.
If i was closer i'd be happy to help , but wales is a goodly long way from devon - I'll have an ask around and see if i can find you some contacts