A piece of material from my golf trolley has got stuck in the lock - now unable to open Boot. Dashboard warning that Boot is open. Can you help, please?

Central locking motor for the boot latch may be stuck open. If it also use cable type release, that lever may be stuck at release position.

The sensor is located and probably built into the boot latch. The sensor is good because the light goes off if you close it slowly. the latch is just worn out with that particular part. Replace the latch. It is not hard to replace if you have a few hand tools.

The problem will be the 'door open sensor' switch. It is out of sight inside the door latch area. This video shows where it is.
http://www.youtube.com/watch?v=BB7o_9MPu4o

The ESP system means the Electronic Stability Program. If the ESP lights on the dashboard permanently the ESP system is faulty. You must access the ESP Electronic Control Unit (ECU) memory for pull out all DTC (Diagnostic Trouble Codes), using diagnostic equipment connected to the data link connector of the car (placed in dashboard, under a plastic cover above the ashtray). Then you will be full informed about bad pieces (e.g.: front right wheel abs sensor interrupted, ...). After bad pieces replacement you will be able to erase all faults memored by ESP ECU, in other words reset the ESP system and turn off the warning lamp on dashboard.

have somebody pull up on the trunk while you press the button inside

sounds like your convenience module is on the fritz

Get hold of a can of Plus Gas or even WD40

Open the slot where the key goes into with a thin screw driver push the thin tube on the can then into the hole

Cover with a piece of tissue , give it a god blast and leave it for a few hours

Do it again and this time gently rock the key as if you are trying to opem the boot

It should free off

As they say if you dont use it you lose it !

change door locks thats all u can do

Unable to open the boot on my 1999 vw passatt either by the remote or using the key. How can I open the boot from the inside?

There is a release in the boot (trunk).  It's a little green piece of the plastic about 12mm diameter that is stuck in the trunk lining just on the other side of the fuel filler.  Pry it out of the liner and pull on it.  That should open the fuel door.