I'm currently replacing the bulbs in the OBC. I read some threads and ordered the type from the wiki but the size is different to the ones already fitted
Would they be okay to use and any thoughts as to why they are a different size?
That looks like suitable bulbs, if a little expensive. The one's I use are : http://cpc.farnell.com/sli-ebt/715-004/ ... dp/SC00338
The physical size of the bulbs is irrelevant, as long as they're noot too big to physically fit in the space available.