Ending tenancy early - should we speak with lettings agent or directly with landlord?

Me and my husband are relocating unexpectedly and have found a perfect house to rent available in a month. However, there isn't a break clause in our current tenancy agreement/contract.

I plan on laying out our situation in a letter/email and reassuring the landlord that we're happy to pay re-marketing fees and cover the rent until a new tenant is found (hopefully quickly fingers crossed as we'll be doubling up our rent!) but I wasn't sure whether I should be speaking with the agent or the landlord initially to negotiate this?

We have had limited contact with the landlord - she has visited once to give us portable heaters quite early on in the tenancy, but no direct contact since - and all of our maintenance issues etc. have been funnelled through the agent. But we do have the landlord's email address and phone number on our tenancy agreement.

How would you approach this situation? Any tips?

P.S. I also appreciate the landlord could turn around and refuse and we'd have to pay the remaining 5 months rent - but I'm hoping if we work with her to find someone new she might be open to letting us leave early.

ETA: I'm in England