What would you do with it?

Put it outside their door. You've done all you can.

To be perfectly honest, if these people are that rude that they can't be bothered, then I would keep the box( no matter what was in it) and if/when they do come round I would tell them I had left it outside their door.

If you know someone leaves at 6.30 in the morning, you must be awake, so I would suggest if you really, want to get rid of the parcel, put your dressing gown on, and take it to the house just as the person is leaving - it gives it's own message. (No idea where this typeface came from must check it out!).

As you say jollyg there will in all probability be an email address on the parcel.
If not and the 7 days go by I would feel quite justified in opening the parcel and getting the company details off the shipping note. It is highly possible that rather than have the parcel shipped back to them the company will allow you to keep it if you have made a note of all your efforts to contact your neighbours. You never know and I have known this to happen! Then you can enjoy with a clear conscience.

In the past I have taken parcels etc in, and asked the courier to inform the recipients. They did not, and now the company is defunct. I had to inform.

One person did not reply to the couriers, so I posted the letter in the bin.

Madam came round about 3 weeks later, so I told her what I had done.

Not best pleased.

Now I do not take anything in at all.

Synon . The address should have senders details on it. Send them an email

It is not yours to do anything other than hand it over to the owners, you are the temporary custodian on your neighbours' behalf.
Put your own note through their door telling them that you have tried to contact them to tell them of their parcel which is in your house. If no reply is received you will assume that it is in order for you to arrange for the parcel to be returned to the sender if you don't hear from them within 7 days.
This is reasonable after you have already taken care of it for 10 days.

Put a note through their door asking them to collect the parcel as soon as possible as it is rather large and in the way.
If nothing happens leave on front step. You could try about 6. I5 am. Just before he goes to work.
Then go back to bed.
At least you would be rid of it!
I take it that you will not be accepting any more parcels on their behalf.
On a different note have you actually seen them leave the house ?
Are they ok?

I did put a note through the door the last time I called round, the day before yesterday.

Could you pop a note through their door asking them to collect it. It's possible the courier didn't put a note in. Other than that I think the only thing you can do is leave it outside, if you had an idea of his return time you could perhaps leave it just before he is due back. Might give you a bottle to say "thank you"!!

Great idea whitewave - would it be legal I wonder? I mean if I give them notice then can I assume they have abandoned it and claim ownership myself

I agree with whitewave, but the wine would probably be wasted on me as I'll drink almost anything!

Note in door saying please collect within 3 days or you will be forced to drink it. Then offer to post the results of your wine tasting through their letter box.