The experience of working closely with another research team will be of enormous benefit to your own research and also very rewarding for you personally.
Are you a PhD student at UCL wishing to spend time at another university doing scientific research and/or training?
Your supervisor and the other members of your supervisory panel will be able to put you in touch with the right people through their own network of contacts. If you already have a co-supervisor at another university, he/she may be able to include you in his/her own research team.
Once you have found another university, make sure that you receive an official letter of invitation. This will ensure that your visit there goes smoothly.