I'm trying to work out the best approach for heating a barn conversion
and I'd appreciate some help/advice/comment:

The layout is as follows: The barn is 30 metres from the house and
about 40 metres (in the opposite direction) from the nearest road (and
mains gas/electricity supply). It will have 2 rooms downstairs and 2
rooms upstairs and the area of the building is 60-70 square metres.
It's 400 years old and we want to avoid running unecessary pipes.
Bear with me...

The original plan was to only put electricity (no gas/oil) down to the
barn and share the main house supply with the barn. The supply would
be fed using thick, armoured cable (4-5cm diameter - can't remember
name) down to the barn. The supply cannot be buried in the path (due
to listed building restrictions - and cost! - but will be hidden from
view and being chopped into by spades, by a stone/cement hood). We
would use a heatstick boiler for the two zone wet UFH and have
separate oil filled radiators for upstairs.

However, an electrician has said that a domestic 100A electricity
supply will not be sufficient to be shared between the main house and
the barn and that we should consider having a separate electricity
supply installed to the barn. This would need to be run from the road
at the bottom of the garden, approx 40 metres! Another alternative
would be to have a second phase installed to the house and the barn
feed taken from that.

The latter is probably the cheaper option but we still have to pay for
the feed from the house to the barn whereas a new connection would be
straight to the barn.

My questions a
1) Are the alternatives to the above solutions?
2) Are heatsticks our only option if we decide to go solely electric?
3) Given the increased running costs of an all electric solution would
it (in the long run) make sense to have a gas or an oil supply put in?
I'm assuming that a gas supply would have to go underground and up
through the garden (like the mains electricity supply) and therefore
be expensive but if we had an oil tank fitted at the foot of the
garden oil could be piped up using a 12mm pipe run above ground.

As you can see, I'm in need of some experience/clarity of thought. Any
assistance will be greatfully received!

Crom