Not unless the work is actually going to increase the value of the house, if it's just redecoration as such then you are unlikely to be able to add it on to the mortgage, otherwise they might give you a personal loan for it but 50k would be a bit much without security.
For example, lets say you were buying a house for 150k and after 50k of work the house would be worth 200k then the bank might consider giving you max mortgage on the 200k finished value. However that work would be subject to stage payment drawdowns and you would have to submit estimates etc for it together with the mortgage application so that when the valuation of the property is being done the valuer could confirm that the finished value will be 200k. Wouldn't cover basic stuff like floors/paint and the like, would probably need to be fairly major renovation.