Ds is doing 7+ in West London too.
Some schools send out past papers, some are very protective of their exam process, and do not!
Waterstones sell lots of books and some past SATS papers. I was advised by ds' school to look for key stage one, level three.
Was also advised that Bond papers can be quite easy.
Mental arithmatic can be done at any time, times tables, simple addition and subtraction.
Also, reading books and identifying words that are unfamiliar and then looking up what they mean in the dictionary.
Ds has done some of his set homework and also a few bits and bobs from books I have purchased.
I would much rather 'keep on top' of all he has learnt this past term than let him go through the first couple of weeks at school stuggling because he has fogotten everything.
Needless to say, he has only done stuff when he has been happy to do so. Has had plenty of time for his playstation, making a mess with his toys and eating all sorts of unsuitable things!