Most of the time I'm splitting, it's for social meals (e.g. large groups of friends and their families) rather than work ones (we all work for the same company, so whoever wants the miles most pays, and that's usually me ) So we usually do a rough calculation, put multiple cards on the table, and tell the waiter to put x amount on this card, y on this one, etc (it's paid by chip&pin at the table anyway).

Only once did a restaurant grumble about it, but we politely made it clear that this was the only way they were going to get their money.