hello flanajb,
1. "I assume you can take a 32 amp feed directly off your home supply without too much expense."
Don't see why not, but i'm not an electrician. Answer will probably depend on the power rating of the machine you intend to run.
2. "Trouble is, running a 4 sided planer / moulder from a garage might cause an issue with the neighbours"
THere's no obvious reason why this should be an issue for a 4 sided planer more than for any other normal woodworking machine. Most modern machines meeting HSE spec will come in at about 85db, so in this regard a 4sideplaner is no different to a spindle moulder, or panelsaw, etc.
The main issue for noise nuisance with neighbours seems to be when using (your)domestic premises for commmercial work. But that aside the normal considerations apply eg working in an enclosed area (building ) to reduce your noise pollution ; not working unnecessarily early/ late in the day ; etc. Local considerations will also apply - if your neighbours are v close to the workshop noise is more of an issue ; also if they are in all day eg retired, or sleep daytime (shift work) - if you can arrange to fit in noisy work when they are mostly absent the problem is solved. These days the council has to measure your noise levels from the location of the complainants premises over a period (1 or weeks) to have an evidential basis for pursuing or dropping a neghbours complaint about workshop noise from domestic premises, so even with a complaint you may be within what is acceptable.
Hope this helps, regards, Catface