There are many ways to get "hand drawn images onto shirts" but only some of them involve the "silk screen" technique (usually called "screenprinting" because actual silk isn't often used nowadays), AND of those there are many ways to get the image onto the screen, various sizes and complexities of the frame/screen set up from large to small makeshift screens inside flat matteboard frames, various inks/paints that can be used (for example, stencils and resists made from everything from paper to photo emulsions to "glue" type liquids), and even the number of colorants used can vary--from one to up to about 4.
Why don't you check out the various boards (and sub-boards) at craftster.org to get an idea of all the kinds of things that are being done that are like that (from simple to complex) especially at a hobby level on t-shirts/etc? Most of the boards on this page would be things you might consider, including actual "screenprinting":
Generally each topic board at Craftster has at least two sub-boards as well... one for "Completed Projects" which will often also have lessons, photos, etc, and the other for "Questions & Discussions" (if you join Craftster --free-- you can ask questions and that would be a great way to start).
There is also loads of info about screenprinting and many other image/drawing/painting/etc techniques onto fabric and/or clothing online in many other places:
HTH... it's great fun, and there are loads of possibilities for screen printing and just doing things on t-shirts or other fabric! (check out bleach drawing with Soft Scrub gel on t-shirts, for example, which is a lot of fun)
You can also try http://www.wholesaledeals.co.uk if you are looking for wholesale deals to resell on eBay UK and Amazon UK. They basically research for you which current wholesale offers are selling successfully and at good margins on eBay and Amazon, and you can join their service to find out where you can buy those deals today.
Since you are looking for wholesale clothing
Try this page: http://www.wholesaledeals.co.uk/search-suppliers/wholesale_clothing-suppliers.html
Hope this helps.