140 miles in one day?

+lots not riding it alone.

I've done a few longer cycles, mostly about 80-90miles but one was a double century (200miles) with a friend. We did it for fun (!).

We averaged just under 17mph (12hrs of cycling time) but then we were doing it as a challenge. I'd say that bike fit is incredibly important - mine is not the best and I had various numb bits afterwards. I had a problem with numb toes since I was using SPDs and touring shoes so the cleat was pressing slightly into my foot. I also got bad shoulder ache from just letting my back rest forward on my arms.

Planning a route that goes past several villages with shops is a very good idea so you can refill water bottles and food supplies.

A few useful points.
I used GPS to navigate (much easier).
I broke 3 spokes on my rear wheel - check it before you go, maybe take some spares too.
I couldn't go near sweet food by the end of the cycle.
Padded shorts = essential.
Repair kit = essential.

(If you're interested http://www.jwshale.com/cycling/doublec/doublec.html )

Hope this is useful.

Looks like a good route.... quite flat where I used to live in Willingham. I take it this wasn't single speed?