i work for them and have used them.
couriers have a couple of days to deliver your parcel, i think 3 days. if you are in an area where they only have 1 or two deliveries they may carry it over to the next day for when they have more in that area. they are self employed so manage their own stuff.
i used the myhermes a couple of times and all have been delivered within 3 days including pickup day.
just package your item well and it will be fine and fully trackable. some people send stuff back in stupid packaging and wonder why it gets broken, ive seen tvs with just a bin bag over them, 50+ cds for music magpie send back in a bin bag, full computer towers with just the label stuck on the case.