Nest Scheme - Biomass - Want it replaced with oil

Does anyone have any experience in dealing with Nest Wales. We took advantage of the scheme back in 2014 and had a biomass boiler installed upon their recommendation. We now believe that we were given inappropriate advice and want the boiler taken out and to revert back to an oil one. Our main concerns are the cost of maintenance (bearing in mind we were able to take advantage of the scheme due to low income, which is still the case), the physical aspect of taking delivery and storing pellets and cleaning out the boiler (bearing in mind my husband was just out of hospital and had been left partially disabled following an accident) and the worry that going forward into older age we won't be able to manage the whole aspect of having a biomass boiler. Some of our concerns could be argued as naivity (how else do you think you're going to get a tonne of pellets from the bottom of your drive to round the back of the house apart from carrying them !!!!), but at no point was it explained to us the bigger picture of running it especially as we had moved here having only known mains gas boilers. To top it all off we have had to pay £600 in service and repair bills since the start of 2018 and now can't afford to repair it following its breakdown yesterday - billowing back smoke.
So, if anyone could offer some constructive advice on how to approach the subject or indeed know of anyone who has successfully had their biomass boiler re-replaced under this scheme (as I've heard rumours that there have been people), I would be very much grateful.