Rallies - facilities?

We were considering going along to a rally next year (our first) but wondered what sort of facilities there are to offer.  We are new (ish) to caravanning, following years of avid camping and so even though we have a battery, although have no idea how long this will last, wondered if showers, toilets, water, electricity are often/ever included in the rallies or is it 'just a field'.  I appreciate different rallies may have different offerings but if we only wanted showers, toilets, water, electricity are there any particular rallies where these are offered?  We are based in the South East, West Sussex to be exact so looking for something nearish for our first if possible.