As RB said as responsible company would ensure the personal development of their employees. The cost of training and then retention of staff, is an issue, but something a said responsible company would see the two go hand in hand.
OP, presumably you were employed by this company to fulfil a certain role within the organisation, and have a written or verbal contract to that extent. If your role has change over the course of time, with the expectation for you to carry out different activities, which you are not competent to do, either through lack of training or experience, may subject the employer to litigation and possible prosecution by H&S, should anything go wrong. The H&S Act places a responsibility on all employers
"to ensure, so far as is reasonably practicable, the health, safety and welfare at work" of all their employees''.
If you have an annual appraisal, and you do not feel you are competent to carry out this new role, you should raise and document that then. Training doesn't have to be outsourced, and can take place in-house, and doesn't need to be formal to be effective.
If you do not have such a system, and you are concerned about doing this work without suitable training, then perhaps find a new employer.
You could seek some guidance from
Contact the Health and Safety Executive - http://www.hse.gov.uk/contact/