Good old ebay! dont know why i never thought to look there, cheers.
When you refer to "they" getting funny, who are you refering to?
Putting a few flared holes in it probably will weaken the crossmember slightly but if you consider how thick it is in the first place.
Could be wrong but I recon Renault want to spread an impact across the front of the car and therefor send it down both chassis legs hence why that bit is so strong, if it writes the car off they're not bothered, it's all about occupant safety. With a cage, proper seat and harness, things are a little different, i'd rather any damage was localised.
I'm keeping the plastic crumple bits, in the event of a relatively light impact there's a chance those could avoid or minimise any metal damage.