Hi ByBox,
You're right; you do need more lockers. But location is critical. I have put in various locations where I have lived and commuted mainly in North and West Yorkshire. The bybox points are not convienient at all. I think you need to research areas extremely carefully. I think your chosen locations proves to be a lack of insight.
Example: I put in York to find the nearest bybox. The closest bybox is in Harrogate. Harrogate is a town for affluent families and tourists. Why would professionals need to use the service when most likely their partner will be at home. Fair enough not everyone in Harrogate has the luxury of one partner staying at home but I bet you they probably have secretaries. Harrogate really isn't a place where there are single, young, professional commuters either. I was surprised to see York not having a central bybox. I know York is a honey pot for tourists but it's a city.
"We try to install them in friendly places that people will go passed on their daily route. The reason for this is because collecting a parcel from a ByBox on your daily route is 83% more carbon efficient than waiting in for the delivery driver. Might sound like green washing but happens to be true. Which is why we try to find places that are safe, with 24/7 access, with good transport links nearby (so either a motorway or train station)."
I'm currently living in Leeds at the moment. The nearest bybox to me is Hunslet. It's definitely not on my commute and I wouldn't venture out of my way so far to do so. I do not feel it is a safe area. Hunslet is near the M621 so you're correct a lot of commuters will use the (short) motorway link. Great for people who drive cars. Absolute pain if you don't. And the motorway is on the south side of the city and Leeds has quite a big one way system route. Another traffic jam at 5pm? No thanks.
(Locations I put in; York, Harrogate, Leeds, Guiseley, Ilkley, Scarcroft.)
So aside from all that, I like to feel I have been provided a special service. I am not sure what special service the bybox lockers are going to provide for me. I feel like the bybox delivery service is only doing half a job. Ideally, from a hard day at work, I like to come home to suburbia to find my package at home waiting for me or the postal slip saying they tried to deliver it. It wouldn't take me long at all to go my local post office pick up point and collect the parcel or ask for a re-delivery.
Ideally, I would love to pick up the phone and say, "I'm home now, please may you deliver my parcel." And within half an hour, just like a take away service, it comes to me. That would be some excellent customer service.
Now I know you are concerned about the carbon emissions. But let's be honest it probably saves a whole lot of money not providing a straight-to-the-home delivery service. But I would spend more money on petrol etc collecting the parcel and spending my time doing so. Time = Money.
I would try putting the bybox lockers very close to train stations, petrol stations, airports and city centres if you're aiming it to commuters. And lots of them.
I've said the above quite quickly and lightly however this isn't a forum about how to improve your business and services. Good luck.