Bike is due its MOT on March 1st, my tax and insurance due 1st April, is it legally possible to let the mot lapse until say March 30th, the bike isn't being ridden, but isn't sorned, i'd just like to get all three lumped together is it doable ?
As long as it not being ridden on the road it's ok! All you will need to do is book an mot when the times comes as if you're stopped you're only covered by insurance if going to an mot station, if it's not booked and stopped by police it'll be a fine
As stated, providing the bike is insured, you are allowed to ride od rive any vehicle without an MOT to a pre-arranged MOT test. If it fails, and providing it is not failed for being or considered to be in a dangerous condition, then you are also permitted to ride the bike home again or to a place of repair, but you must go by the most direct route.
I maybe wrong but might be worth checking is your insurance not void if you do not have an MOT, unless it is booked into the station and you ride directly to and from the MOT. Just a thought for during the period the bike will be sat with no MOT.
Insurers cannot null and void a policy under the circumstances you mention unless it is specifically stated in the terms and conditions. The only time it could have a bearing is in the event of a crash and the vehicle was deemed a total loss, they use the lack of a current MOT to beat down the valuation, but then a reasonable argument as part of your uninsured losses claim (assuming it was not your fault) would be that you were heading to a pre-arranged MOT, it was expected to pass and therefore full valuation would apply.