if I ever lose my 'key' for the locking nuts
It is very kind of your friend to offer to weld a nut on your bolt if you loose your locking key.
However, I would be concerned about damage caused to the diamond cut alloy in the process.
A refurb / replacement wheel is NOT a cheap option, and the welding option is a lot of good if you have a puncture a long way from home.
If you are like my son, who has lost more keys in ten years than anybody I know !.
Then it maybe a good idea to send for a spare locking wheel nut key before this happens ?.
The removal key / sockets do have different random coded pattern in the head and are coloured coded with a blob of paint on the master key ( black / purple etc ) and a spare key nut CAN be purchased / ordered from the main dealer.
Because of this, they are not cheap at £29 each.
Here is a link to the replacement key / socket for the black coded set.
Locking Wheel Nut Key 173 Black 10296779 in Service Parts Locking Wheel Nuts
www.ukmgparts.com
But remember, the main dealer RRP price for a complete set is £60 and not £26.95 .
A complete set of bolts and nuts can be purchased on-line for this price.
If you have proof of purchase of your previous set from the SAME company, then you know what you need to do !.
Request a set with the same code / colour ( if in stock ) and then you have a spare key / socket and an additional set of replacement bolts in for the price.
Two sets are STILL less expensive than buying direct from most main dealers.