Is that the first document/notice you've received?
In particular, did you ever receive a "Notice of Enforcement" from Marston?
The bailiff must have a warrant to enforce. Before they do so they need to serve a Notice of Enforcement giving you seven clear days to pay. I suspect that all of the statutory notices and the NoE have gone to your previous address. Marston's have then traced your current address. They should have informed TFL who would then apply to the Traffic Enforcement Centre at Northampton County Court for the warrant to be resealed (reissued) with the new address.
Without a valid warrant at the correct name and address the bailiff cannot enforce. They can however clamp your vehicle if found in a public place. I suspect that Marston do not (yet) have a valid warrant. But I might be wrong.
Why are you so vague about dates? It doesn't give a good impression.
Waht is the:
Date of contravention?
Date of PCN, if known?
Date of moving out of home?
Date of travel abroad?
Date of return from abroad?
Date of moving into new home?
Date of change of address on V5c registration doc (doc ref date)?
You'll need to submit a Statutory Declaration to the effect that you did not receive the original Penalty Charge Notice together with an Out of Time application to the TEC at Northampton County Court. You'll need a snappy concise reason as to why you're late otherwise TFL will object and your SD will be refused.
I suggest that you contact
Bailiff Advice Online for guidance on how to handle the bailiff and what to put on the OoT application. Don't attempt an OoT with advice from BAO and/or this forum.
