I own a 51RI p-bass & the weight is no issue. It's one of the best basses I've ever owned. Having been used to standard shaped P-basses I didn't find too much of an adjustment.
My only thoughts on a Rickenbacker are they are a lot of money to spend if like me you decide you a Fender player through & through. Seeing as you are based in Wilts, last time I went to Swindon they had some great looking Rickenfakkers in a couple of guitar shops that were just under £500. So you could get a nice Fender and try one of these? Just a thought. I'd imagine the resale value would hold too.