My Worcester 28Si boiler is leaking?

I have to keep putting up the pressure in my boiler, every day and now twice a day. The problem now is that it has started to drip when I do this and quite badly as well, the water coming out is hot. Does this require a new part or is it something I or my husband can fix (bearing in mind he is a joiner). I know Worcester engineers are really good its just the cost !

Thanks