Hi Tazz
Going to Shenzhen is q simple. You can get a train from the Kowloon side, the fares is around $40 - 80 return depending on which class you travel on.
The journey takes around 45 minutes to an hour, may be less, it depends where about you're staying?
It's handy to have some HK$ as well as US$ ready before you depart UK, don't need much, around 100 pounds will be more than adequate, then you can change some when you get to HK.
I would not advice you to post anything from Shenzhen, do it in HK if I were you. If you're staying in HK, then perhaps take a massive suitcase and take it to Shenzhen for short trips.
I may have some ideas where to look for new supplies.
If you're intertesed let me know.
