56 plate peugeot boxter van sudden inability to find 1st, 2nd and reverse g?

does anyone please have an idea of how to fix my pug boxter 2.2 hdi. i just spent 350 getting it through the M.O.T. not even 2 hours later was driving along and the gear lever just seemed to fall from its normal position while in 2nd and try as i might it stuck there. i couldnt get help where i was so decided i would have to encourage it out of its position which it eventually did, it started, and it went into what turned out to be 3rd gear, it allowed me to go back down to 2nd and away, but then it again wouldnt let me find 1st or 2nd a short while later and it also got stuck in reverse a little after that, and all this without any clutch probs or noticeable gearbox issues, please help guys i just started working with a guy who has loads of work for me and i cant afford to let him down nor pay a garage as have been out of work prior to this for 2 years. thanks.