AL03 Error Code on Hotpoint FDW85 - How do I Fix It?

My dishwasher keeps giving me the error code AL03. I have read some helpful hints and answerson how to sort this issue, but I still keep getting the error code.

To date I have tried:

1) removing the filters, cleaning them, cleaning out the drain hole the filters sit in and taking a sink plunger to it. No luck.

2) removing the outlet hose, running water through it to check for blockages. No luck

3) removing the pump, cleaning it, checking for foriegn objects, puchasing a new pump. Again, no luck.

After trying all the above I started a cycle (eco wash, which is a 2hr cycle). The dishwasher started and all appeared well (it actually drained water, so I thought the pump is working) as it carried on for circa 30 mins before not doing anything and then it gave me the error code again.

I am at a loss now as to what the problem could be. It can't be much as it starts and can pump waste water out. Has anyone got any ideas as to what the problem could be and how to fix it, as I am at the point of calling someone out or buying a new machine?

Thanks in advance of any answers.