I have been there for holidays some time with my partner.
Most of the people have been very nice and many people speak german and/or english.
Because of my work, we always traveled at the end of September or in the begin of October: The weather was around 25-30 degrees. There were not many Croatians swimming in the sea around that time, for them its already too cold, but as english atlantikswimmer it should be no problem for you. ^^ (The family from my mother lived in france at the atlantik shore.) But as these 25 degree are known as "too cold" for swimming, I think it will be very hot in summer.
If you have the possibility to travel outside the typical school holidays, you can easily visit croatia and drive along the shore until you find a place you like. At the end of september only about 30% of the available tourist beds were already sold, so you can easily decide that you first want to see the rooms before you decide to check in. The only Misadvantage: If you like to do special things, that are linked to mass of tourists, these things normally have already closed in the smaller towns. So no Banana boat, parashooting pulled from a boat, .... In June normally, all these things should be already available, but i´d check a hotel before you travel.
From what we have seen on the beaches around summer there seem to be lots of people, so you better check a hotel before coming. In the typical tourists towns there are also bars along the beach with music and so on, so the tourist beaches seem to be very loud in summer. Around everywhere I have seen prospects for sailing school, diving, surfing, banana boat, dinner boat, ...
The croatian food was very good and its also cheap, so my partner paid for a steak with vegetables around EUR 8. The local food is also very good. Only avoid the tourist restaurants that are present at the typical tourist spots at the market and so on. If you see the card outside and evverything is "Hamburger with Frites", "Sausage with Frites", Pizza, .... i would avoid it and walk on into the villages. Drinking was also ok, so Cocktails were around 5 EUR and Beer is between 2 EUR - 3,50 EUR (the local beer with the 2 EUR is "Carlovacko" tasting very similar to Austrian "Märzen" Bier which tastes a bit more bitter then usual beers, additional they have the typical european sorts as Becks, Tuborg, with less taste for more price) ^^ In most Area the water from the tube tastes not very good, so for drinking I´d buy some water in the super markets in croatia.
In most smaller cities you still have traditional markets, so if you have an appartment and cook yourself, its very cheap to buy food. (To austrian standard.) The also sell lots of local fruits, that are also very cheap.
If the weather is not so nice you can visit the towns for typical tourist stuff, shopping, visiting churches, museums, ... they also have lots of roman ruins and ancient history if you are interested in these.
Short: Restaurant Food very well and cheap, with the hotel evening buffet we mostly had no luck. If you want to do party, want music all day at the beach and so on..., try to be around the bigger cities like Split and so on, and try to visit it in the main holiday time. If you like it quiet, best time is September, and then find yourself a spot you like and stay there. (There are also very small villages around the beach with nearly no tourism, only some of the villagers are renting a room. So you have lots of silence and peace there, but must accept that there will be no icecream or sodashop at the beach and so on. ) Lots of national park you can use for hiking, climbing, bicycle or simply walk thorugh nature and so on.
If its important to you: Beside some islands croatia has no sand beaches. (Some hotels have artifical.) But I think this is similar to the british coast.