Items to consider -
1 - don't secure padlock fittings with screws they are a waste of time and can be yanked out with a small bar - use bolts.
2 - make sure any hinges are on the INSIDE else they can just unscew them.
3 - PIRs are as above just a good friendly way to give the thieves light to work by.
4 - use at least two padlocks and imagine you wanted to cut them, can you get a pair of bolt croppers to the hasp ? If so they are useless - get a better one with a sheathed hasp [ they won't be cheap and neither will the fittings].
5 - buy and fit a remote shed alarm [about £30 on E Bay]. The alarm sits in the house and you will hear it - the cheap squeaky toys from B&Q that live in the shed etc are just that - and keep either a pick axe handle or baseball bat by the door [the choice is yours I don't play baseball].
6 - locking the bike down inside is a dead end as once inside they have all the time in the world [and nice and private too] and ANY chain can be cut with big croppers [certainly if they can be braced against the floor].
7 - If you have a window in there fit a grill or at least a couple of bars to make too small to climb through [and make sure it can't be pulled out}.
This lot will NOT be cheap and means a fair bit of work but it's up to you - how much do you REALLY value your bike.
All sound advice with the exception of the PIR light. A permanent on light is no deterrent. One that comes on if you go near the garage attracts attention, specially if you live rural. As my neighbour said "one of your lights kept coming on last night checked but couldn't see anything".
What do you reckon to these alarms particularly the lock alarm
http://www.easyalarms.co.uk/shed_garden_garage_alarms.asp
And this was a silly (at best) remark
"pick axe handle or baseball bat"
You are supplying evidence for the prosecution.
PS long handled items can catch on door frames when you need them.