Noticed quite a few searches ending up here looking for these, so here’s where I’ve got them from if that’s of any use.
For MS221 I used the past papers and solutions from http://open.wibble.to/ .They don’t have any past exam papers for M208, so I purchased and downloaded the pdfs from https://rsm2.rsmsecure.com/ousacart/webstore/store.php?itemsearch=M208 (they also have more up to date exam papers for MS221) . The solutions for these past M208 papers were posted by the tutors in the M208 forums. I’ve also read good reports on the solution booklets for MS221 and M208 from Black Badge Press but haven’t personally used any of their materials.
Please note that all the solutions referenced above are not ‘official’ solutions, and don’t contain the full marking scheme as the Open University holds the copyrights on those.
There looks to be plenty more stuff dotted around the intertubes, but I can’t vouch for how accurate or usefull it all is.