I've raised £700 to replace an old, leaky, dangerous hot water tank/immersion heater

update 28/07/2018 Our guardian angel has been watching over us and we have the chance of getting this job done for a fraction of the original quote, therefore I am happy to be able to have lowered the amount we need to raise. Big thanks to everyone who has donated so far......I cannot say how much we appreciate it.
Basically, we have no hot water........our hot water tank is old, corroded and leaks. We cannot switch it on as it shorts out our electricity so it is obviously unsafe. It will cost us approximately £3000 to replace the system and the damaged wiring. Our house insurance won't pay out due to the age of the tank. The bank won't grant us a loan due to our current situation.
My husband and I both have disabilities and I am currently on long term sick leave due to a degenerative condition which has over the past few months rapidly deteriorated limiting mobility. My husband has military acquired PTSD and is unable to work due to his mental state and is my carer at this time.
We have applied for several grants and assistance from various groups, none of which are able to offer the help we need, so, as a last resort, we come to you.
We would like to thank you all in advance for your generosity and kindness in assisting strangers to have one of those things that we in the UK take for granted.