Hi OP...
Fellow UK TRT patient here....
They did away with Sustanon a while ago, and now offer Test Enanthate (short ester) or Nebido (Test Undecanoate - long ester)
What you get is purely down to your doc's preference.
I'm personally on Nebido - and it works for me - but Test Enanthate will be better than T-Gels for sure!
As for splitting your doses - you can buy sterile vials on ebay for next to nothing in bulk....
I would transfer your ampoules into the vials and this will make measuring your doses much easier.
There are also loads of sites here in the UK for syringes and needles to buy in bulk, if you want to save the embarrassment of asking your practice nurse for them all the time.
It is common practice for the nurse to ask you to self-inject in their presence once or twice, it wasn't an issue for me.
Hope this helps - good luck bro!